From 6d9552850976bc253a54847ca11813e3cd78c712 Mon Sep 17 00:00:00 2001
From: Zeb Engberg <zebengberg@gmail.com>
Date: Fri, 22 Sep 2023 08:25:32 -0600
Subject: [PATCH] issue consistent ModuleNotFoundErrors for missing
 dependencies

---
 CHANGELOG.md                                  |  5 ++
 pycontrails/core/cache.py                     | 54 ++++++++++------
 pycontrails/core/flight.py                    | 42 ++++++++-----
 pycontrails/core/met.py                       | 21 ++++---
 pycontrails/core/polygon.py                   | 21 +++++--
 pycontrails/core/vector.py                    | 10 ++-
 pycontrails/datalib/ecmwf/era5.py             | 11 ++--
 pycontrails/datalib/ecmwf/hres.py             | 14 +++--
 pycontrails/datalib/gfs/gfs.py                | 31 +++++++---
 pycontrails/ext/bada.py                       |  4 +-
 pycontrails/ext/cirium.py                     |  4 +-
 pycontrails/models/accf.py                    | 20 +++---
 pycontrails/models/cocip/output_formats.py    | 12 ++--
 .../models/cocipgrid/cocip_time_handling.py   | 15 ++---
 pycontrails/utils/dependencies.py             | 62 +++++++++++++++++++
 15 files changed, 231 insertions(+), 95 deletions(-)
 create mode 100644 pycontrails/utils/dependencies.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a988233ba..883761627 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@
 
 - Use the experimental version number parameter `E` in `pycontrails.ecmwf.hres.get_forecast_filename`. Update the logic involved in setting the dissemination data stream indicator `S`.
 
+### Internals
+
+- Provide consistent `ModuleNotFoundError` messages when optional dependencies are not installed.
+- Move the `synthetic_flight` module into the `pycontrails.ext` namespace.
+
 ## v0.47.1
 
 ### Fixes
diff --git a/pycontrails/core/cache.py b/pycontrails/core/cache.py
index 7c9237ee5..44c354bda 100644
--- a/pycontrails/core/cache.py
+++ b/pycontrails/core/cache.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import functools
 import logging
 import os
 import pathlib
@@ -14,20 +15,23 @@
 
 from overrides import overrides
 
+from pycontrails.utils import dependencies
+
 # optional imports
 if TYPE_CHECKING:
     import google
 
 
+@functools.cache
 def _get_user_cache_dir() -> str:
     try:
         import platformdirs
     except ModuleNotFoundError as e:
-        raise ModuleNotFoundError(
-            "Using the pycontrails CacheStore requires the 'platformdirs' package. "
-            "This can be installed with 'pip install pycontrails[ecmwf]' or "
-            "'pip install platformdirs'."
-        ) from e
+        dependencies.raise_module_not_found_error(
+            name="cache module",
+            package_name="platformdirs",
+            module_not_found_error=e,
+        )
     return platformdirs.user_cache_dir("pycontrails")
 
 
@@ -468,10 +472,11 @@ def __init__(
         try:
             from google.cloud import storage
         except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                "GCPCache requires the `google-cloud-storage` module, which can be installed "
-                "using `pip install pycontrails[gcp]`"
-            ) from e
+            dependencies.raise_module_not_found_error(
+                name="GCPCacheStore class",
+                package_name="google-cloud-storage",
+                module_not_found_error=e,
+            )
 
         if "https://" in cache_dir:
             raise ValueError(
@@ -830,11 +835,12 @@ def _upload_with_progress(blob: Any, disk_path: str, timeout: int, chunk_size: i
     try:
         from tqdm.auto import tqdm
     except ModuleNotFoundError as e:
-        raise ModuleNotFoundError(
-            "Method `put` requires the `tqdm` module, which can be installed using "
-            "`pip install pycontrails[gcp]`. "
-            "Alternatively, set instance attribute `show_progress=False`."
-        ) from e
+        dependencies.raise_module_not_found_error(
+            name="_upload_with_progress function",
+            package_name="tqdm",
+            module_not_found_error=e,
+            pycontrails_optional_package="gcp",
+        )
 
     # minimal possible chunk_size to allow nice progress bar
     blob.chunk_size = chunk_size
@@ -852,13 +858,23 @@ def _download_with_progress(
 
     try:
         from google.resumable_media.requests import ChunkedDownload
+    except ModuleNotFoundError as e:
+        dependencies.raise_module_not_found_error(
+            name="_download_with_progress function",
+            package_name="google-cloud-storage",
+            module_not_found_error=e,
+            pycontrails_optional_package="gcp",
+        )
+
+    try:
         from tqdm.auto import tqdm
     except ModuleNotFoundError as e:
-        raise ModuleNotFoundError(
-            "Method `get` requires the `tqdm` and `google-cloud-storage` modules, "
-            "which can be installed using `pip install pycontrails[gcp]`. "
-            "Alternatively, set instance attribute `show_progress=False`."
-        ) from e
+        dependencies.raise_module_not_found_error(
+            name="_download_with_progress function",
+            package_name="tqdm",
+            module_not_found_error=e,
+            pycontrails_optional_package="gcp",
+        )
 
     blob = gcp_cache._bucket.get_blob(gcp_path)
     url = blob._get_download_url(gcp_cache._client)
diff --git a/pycontrails/core/flight.py b/pycontrails/core/flight.py
index a78389587..126344aaf 100644
--- a/pycontrails/core/flight.py
+++ b/pycontrails/core/flight.py
@@ -16,6 +16,7 @@
 from pycontrails.core.fuel import Fuel, JetA
 from pycontrails.core.vector import AttrDict, GeoVectorDataset, VectorDataDict, VectorDataset
 from pycontrails.physics import constants, geo, units
+from pycontrails.utils import dependencies
 
 logger = logging.getLogger(__name__)
 
@@ -533,10 +534,12 @@ def segment_azimuth(self) -> npt.NDArray[np.float_]:
         try:
             import pyproj
         except ModuleNotFoundError as exc:
-            raise ModuleNotFoundError(
-                "The 'segment_azimuth' method requires the 'pyproj' package. "
-                "Install with 'pip install pyproj'."
-            ) from exc
+            dependencies.raise_module_not_found_error(
+                name="Flight.segment_azimuth method",
+                package_name="pyproj",
+                module_not_found_error=exc,
+                pycontrails_optional_package="pyproj",
+            )
 
         geod = pyproj.Geod(a=constants.radius_earth)
         az, *_ = geod.inv(lons1, lats1, lons2, lats2)
@@ -1001,10 +1004,12 @@ def _geodesic_interpolation(self, geodesic_threshold: float) -> pd.DataFrame | N
         try:
             import pyproj
         except ModuleNotFoundError as exc:
-            raise ModuleNotFoundError(
-                "The '_geodesic_interpolation' method requires the 'pyproj' package. "
-                "Install with 'pip install pyproj'."
-            ) from exc
+            dependencies.raise_module_not_found_error(
+                name="Flight._geodesic_interpolation method",
+                package_name="pyproj",
+                module_not_found_error=exc,
+                pycontrails_optional_package="pyproj",
+            )
 
         geod = pyproj.Geod(ellps="WGS84")
         longitudes: list[float] = []
@@ -1138,11 +1143,11 @@ def to_traffic(self) -> "traffic.core.Flight":
         try:
             import traffic.core
         except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                "This requires the 'traffic' module, which can be installed using "
-                "'pip install traffic'. See the installation documentation at "
-                "https://traffic-viz.github.io/installation.html for more information."
-            ) from e
+            dependencies.raise_module_not_found_error(
+                name="Flight.to_traffic method",
+                package_name="traffic",
+                module_not_found_error=e,
+            )
 
         return traffic.core.Flight(
             self.to_dataframe(copy=True).rename(columns={"time": "timestamp"})
@@ -1767,11 +1772,14 @@ def fit_altitude(
     """
     try:
         import pwlf
-    except ModuleNotFoundError:
-        raise ModuleNotFoundError(
-            "The 'fit_altitude' function requires the 'pwlf' package."
-            "This can be installed with 'pip install pwlf'."
+    except ModuleNotFoundError as e:
+        dependencies.raise_module_not_found_error(
+            name="fit_altitude function",
+            package_name="pwlf",
+            module_not_found_error=e,
+            pycontrails_optional_package="pwlf",
         )
+
     for i in range(1, max_segments):
         m2 = pwlf.PiecewiseLinFit(elapsed_time, altitude_ft)
         r = m2.fitfast(i, pop)
diff --git a/pycontrails/core/met.py b/pycontrails/core/met.py
index 7ee0d9ef8..180861548 100644
--- a/pycontrails/core/met.py
+++ b/pycontrails/core/met.py
@@ -36,6 +36,7 @@
 from pycontrails.core.cache import CacheStore, DiskCacheStore
 from pycontrails.core.met_var import AirPressure, Altitude, MetVariable
 from pycontrails.physics import units
+from pycontrails.utils import dependencies
 from pycontrails.utils import temp as temp_module
 
 logger = logging.getLogger(__name__)
@@ -1942,18 +1943,22 @@ def to_polyhedra(
         try:
             from skimage import measure
         except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                "This method requires the `skimage` module from scikit-learn, which can be "
-                "installed using `pip install pycontrails[vis]`"
-            ) from e
+            dependencies.raise_module_not_found_error(
+                name="MetDataArray.to_polyhedra method",
+                package_name="scikit-image",
+                pycontrails_optional_package="vis",
+                module_not_found_error=e,
+            )
 
         try:
             import open3d as o3d
         except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                "This method requires the `open3d` module, which can be installed "
-                "with `pip install pycontrails[open3d]` or `pip install open3d`."
-            ) from e
+            dependencies.raise_module_not_found_error(
+                name="MetDataArray.to_polyhedra method",
+                package_name="open3d",
+                pycontrails_optional_package="open3d",
+                module_not_found_error=e,
+            )
 
         if len(self.data["level"]) == 1:
             raise ValueError(
diff --git a/pycontrails/core/polygon.py b/pycontrails/core/polygon.py
index c507fa7f8..d0da7c6ba 100644
--- a/pycontrails/core/polygon.py
+++ b/pycontrails/core/polygon.py
@@ -14,16 +14,29 @@
 import numpy as np
 import numpy.typing as npt
 
+from pycontrails.utils import dependencies
+
 try:
     import cv2
+except ModuleNotFoundError as exc:
+    dependencies.raise_module_not_found_error(
+        name="polygon module",
+        package_name="opencv-python",
+        module_not_found_error=exc,
+        pycontrails_optional_package="vis",
+    )
+
+try:
     import shapely
     import shapely.geometry
     import shapely.validation
 except ModuleNotFoundError as exc:
-    raise ModuleNotFoundError(
-        "This module requires the 'opencv-python' and 'shapely' packages. "
-        "These can be installed with 'pip install pycontrails[vis]'."
-    ) from exc
+    dependencies.raise_module_not_found_error(
+        name="polygon module",
+        package_name="shapely",
+        module_not_found_error=exc,
+        pycontrails_optional_package="vis",
+    )
 
 
 def buffer_and_clean(
diff --git a/pycontrails/core/vector.py b/pycontrails/core/vector.py
index 5bf7aed80..72f3dec15 100644
--- a/pycontrails/core/vector.py
+++ b/pycontrails/core/vector.py
@@ -17,6 +17,7 @@
 from pycontrails.core import coordinates, interpolation
 from pycontrails.core import met as met_module
 from pycontrails.physics import units
+from pycontrails.utils import dependencies
 from pycontrails.utils import json as json_module
 
 logger = logging.getLogger(__name__)
@@ -1386,9 +1387,12 @@ def transform_crs(
         try:
             import pyproj
         except ModuleNotFoundError as exc:
-            raise ModuleNotFoundError(
-                "Transforming CRS requires the 'pyproj' module. Install with 'pip install pyproj'."
-            ) from exc
+            dependencies.raise_module_not_found_error(
+                name="GeoVectorDataset.transform_crs method",
+                package_name="pyproj",
+                module_not_found_error=exc,
+                pycontrails_optional_package="pyproj",
+            )
 
         transformer = pyproj.Transformer.from_crs(self.attrs["crs"], crs, always_xy=True)
         lon, lat = transformer.transform(self["longitude"], self["latitude"])
diff --git a/pycontrails/datalib/ecmwf/era5.py b/pycontrails/datalib/ecmwf/era5.py
index 04efe41fa..3d03f8507 100644
--- a/pycontrails/datalib/ecmwf/era5.py
+++ b/pycontrails/datalib/ecmwf/era5.py
@@ -28,6 +28,7 @@
     TopNetSolarRadiation,
     TopNetThermalRadiation,
 )
+from pycontrails.utils import dependencies
 from pycontrails.utils.temp import temp_file
 
 if TYPE_CHECKING:
@@ -497,10 +498,12 @@ def _download_file(self, times: list[datetime]) -> None:
                 try:
                     import cdsapi
                 except ModuleNotFoundError as e:
-                    raise ModuleNotFoundError(
-                        "Some `ecmwf` module dependencies are missing. "
-                        "Please install all required dependencies using `pip install -e .[ecmwf]`"
-                    ) from e
+                    dependencies.raise_module_not_found_error(
+                        name="ERA5._download_file method",
+                        package_name="cdsapi",
+                        module_not_found_error=e,
+                        pycontrails_optional_package="ecmwf",
+                    )
 
                 try:
                     self.cds = cdsapi.Client(url=self.url, key=self.key)
diff --git a/pycontrails/datalib/ecmwf/hres.py b/pycontrails/datalib/ecmwf/hres.py
index 86eb64697..6245f770e 100644
--- a/pycontrails/datalib/ecmwf/hres.py
+++ b/pycontrails/datalib/ecmwf/hres.py
@@ -27,7 +27,7 @@
     TopNetSolarRadiation,
     TopNetThermalRadiation,
 )
-from pycontrails.utils.iteration import chunk_list
+from pycontrails.utils import dependencies, iteration
 from pycontrails.utils.temp import temp_file
 from pycontrails.utils.types import DatetimeLike
 
@@ -271,10 +271,12 @@ def __init__(
         try:
             from ecmwfapi import ECMWFService
         except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                "Some `ecmwf` module dependencies are missing. "
-                "Please install all required dependencies using `pip install -e .[ecmwf]`"
-            ) from e
+            dependencies.raise_module_not_found_error(
+                name="HRES class",
+                package_name="ecmwf-api-client",
+                module_not_found_error=e,
+                pycontrails_optional_package="ecmwf",
+            )
 
         # constants
         # ERA5 now delays creating the server attribute until it is needed to download
@@ -596,7 +598,7 @@ def download_dataset(self, times: list[datetime]) -> None:
 
         # download in sets of 24
         if len(steps) > 24:
-            for _steps in chunk_list(steps, 24):
+            for _steps in iteration.chunk_list(steps, 24):
                 self._download_file(_steps)
         elif len(steps) > 0:
             self._download_file(steps)
diff --git a/pycontrails/datalib/gfs/gfs.py b/pycontrails/datalib/gfs/gfs.py
index 3c7fe8daf..b35caf531 100644
--- a/pycontrails/datalib/gfs/gfs.py
+++ b/pycontrails/datalib/gfs/gfs.py
@@ -30,6 +30,7 @@
     TOAUpwardShortwaveRadiation,
     Visibility,
 )
+from pycontrails.utils import dependencies
 from pycontrails.utils.temp import temp_file
 from pycontrails.utils.types import DatetimeLike
 
@@ -135,12 +136,23 @@ def __init__(
     ):
         try:
             import boto3
+        except ModuleNotFoundError as e:
+            dependencies.raise_module_not_found_error(
+                name="GFSForecast class",
+                package_name="boto3",
+                module_not_found_error=e,
+                pycontrails_optional_package="gfs",
+            )
+
+        try:
             import botocore
         except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                "`gfs` module dependencies are missing. "
-                "Please install all required dependencies using `pip install -e .[gfs]`"
-            ) from e
+            dependencies.raise_module_not_found_error(
+                name="GFSForecast class",
+                package_name="botocore",
+                module_not_found_error=e,
+                pycontrails_optional_package="gfs",
+            )
 
         # inputs
         self.paths = paths
@@ -650,11 +662,12 @@ def _download_with_progress(
     try:
         from tqdm import tqdm
     except ModuleNotFoundError as e:
-        raise ModuleNotFoundError(
-            "Download with progress requires the `tqdm` module, "
-            "which can be installed using `pip install pycontrails[gfs]`. "
-            "Alternatively, set instance attribute `show_progress=False`."
-        ) from e
+        dependencies.raise_module_not_found_error(
+            name="_download_with_progress function",
+            package_name="tqdm",
+            module_not_found_error=e,
+            pycontrails_optional_package="gfs",
+        )
 
     meta = client.head_object(Bucket=bucket, Key=key)
     filesize = meta["ContentLength"]
diff --git a/pycontrails/ext/bada.py b/pycontrails/ext/bada.py
index 4248fcb45..6f0426da4 100644
--- a/pycontrails/ext/bada.py
+++ b/pycontrails/ext/bada.py
@@ -22,8 +22,8 @@
 
 except ImportError as e:
     raise ImportError(
-        'Failed to import `pycontrails-bada` extension. Install with `pip install "pycontrails-bada'
-        ' @ git+ssh://git@github.com/contrailcirrus/pycontrails-bada.git"`'
+        "Failed to import the 'pycontrails-bada' package. Install with 'pip install"
+        ' "pycontrails-bada @ git+ssh://git@github.com/contrailcirrus/pycontrails-bada.git"\'.'
     ) from e
 else:
     __all__ = [
diff --git a/pycontrails/ext/cirium.py b/pycontrails/ext/cirium.py
index 3342684c4..448f5f4e7 100644
--- a/pycontrails/ext/cirium.py
+++ b/pycontrails/ext/cirium.py
@@ -7,8 +7,8 @@
 
 except ImportError as e:
     raise ImportError(
-        "Failed to import `pycontrails-cirium` extension. Install with `pip install"
-        ' "pycontrails-cirium @ git+ssh://git@github.com/contrailcirrus/pycontrails-cirium.git"`'
+        "Failed to import the 'pycontrails-cirium' package. Install with 'pip install"
+        ' "pycontrails-cirium @ git+ssh://git@github.com/contrailcirrus/pycontrails-cirium.git"\'.'
     ) from e
 else:
     __all__ = ["Cirium"]
diff --git a/pycontrails/models/accf.py b/pycontrails/models/accf.py
index 392a1cc0e..041e3dffd 100644
--- a/pycontrails/models/accf.py
+++ b/pycontrails/models/accf.py
@@ -21,6 +21,7 @@
 from pycontrails.core.models import Model, ModelParams
 from pycontrails.core.vector import GeoVectorDataset
 from pycontrails.datalib import ecmwf
+from pycontrails.utils import dependencies
 
 WideBodyJets = {
     "A332",
@@ -143,14 +144,6 @@ def __init__(
         params: dict[str, Any] = {},
         **params_kwargs: Any,
     ) -> None:
-        try:
-            import climaccf  # noqa: F401
-        except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                "Requires the climaccf package which can be installed"
-                "using pip install pycontrails[accf]"
-            ) from e
-
         # Normalize ECMWF variables
         met = standardize_variables(met, self.met_variables)
 
@@ -213,8 +206,15 @@ def eval(
         NotImplementedError
             Raises if input ``source`` is not supported.
         """
-
-        from climaccf.accf import GeTaCCFs
+        try:
+            from climaccf.accf import GeTaCCFs
+        except ModuleNotFoundError as e:
+            dependencies.raise_module_not_found_error(
+                name="ACCF.eval method",
+                package_name="climaccf",
+                module_not_found_error=e,
+                pycontrails_optional_package="accf",
+            )
 
         self.update_params(params)
         self.set_source(source)
diff --git a/pycontrails/models/cocip/output_formats.py b/pycontrails/models/cocip/output_formats.py
index 119d088e9..039dd26f2 100644
--- a/pycontrails/models/cocip/output_formats.py
+++ b/pycontrails/models/cocip/output_formats.py
@@ -31,8 +31,8 @@
 from pycontrails.models.cocip.radiative_forcing import albedo
 from pycontrails.models.humidity_scaling import HumidityScaling
 from pycontrails.models.tau_cirrus import tau_cirrus
-from pycontrails.physics import geo, units
-from pycontrails.physics.thermo import rho_d
+from pycontrails.physics import geo, thermo, units
+from pycontrails.utils import dependencies
 
 # -----------------------
 # Flight waypoint outputs
@@ -920,7 +920,7 @@ def time_slice_statistics(
         * flight_waypoints["segment_length"]
     )
     contrails["pressure"] = units.m_to_pl(contrails["altitude"])
-    contrails["rho_air"] = rho_d(contrails["air_temperature"], contrails["pressure"])
+    contrails["rho_air"] = thermo.rho_d(contrails["air_temperature"], contrails["pressure"])
     contrails["plume_mass_per_m"] = plume_mass_per_distance(
         contrails["area_eff"], contrails["rho_air"]
     )
@@ -1586,7 +1586,11 @@ def contrails_to_hi_res_grid(
     try:
         from tqdm.auto import tqdm
     except ModuleNotFoundError as exc:
-        raise ModuleNotFoundError("Install the 'tqdm' package") from exc
+        dependencies.raise_module_not_found_error(
+            name="contrails_to_hi_res_grid function",
+            package_name="tqdm",
+            module_not_found_error=exc,
+        )
 
     for i in tqdm(heads_t.index[:2000]):
         contrail_segment = GeoVectorDataset(
diff --git a/pycontrails/models/cocipgrid/cocip_time_handling.py b/pycontrails/models/cocipgrid/cocip_time_handling.py
index b4b385156..ad3c14c99 100644
--- a/pycontrails/models/cocipgrid/cocip_time_handling.py
+++ b/pycontrails/models/cocipgrid/cocip_time_handling.py
@@ -15,6 +15,7 @@
 from pycontrails.core.met import MetDataset
 from pycontrails.core.vector import GeoVectorDataset
 from pycontrails.models.cocip import cocip
+from pycontrails.utils import dependencies
 
 if TYPE_CHECKING:
     import tqdm
@@ -159,13 +160,13 @@ def init_pbar(self) -> "tqdm.tqdm" | None:
 
         try:
             from tqdm.auto import tqdm
-        except ModuleNotFoundError as e:
-            raise ModuleNotFoundError(
-                f"Running model {type(self).__name__}  with parameter "
-                "show_progress=True requires the 'tqdm' module, which can be "
-                "installed with 'pip install tqdm'. "
-                "Alternatively, set model parameter 'show_progress=False'."
-            ) from e
+        except ModuleNotFoundError as exc:
+            dependencies.raise_module_not_found_error(
+                name="CocipGrid.init_pbar method",
+                package_name="tqdm",
+                module_not_found_error=exc,
+                extra="Alternatively, set model parameter 'show_progress=False'.",
+            )
 
         estimate = self._estimate_runtime()
 
diff --git a/pycontrails/utils/dependencies.py b/pycontrails/utils/dependencies.py
new file mode 100644
index 000000000..8c918194a
--- /dev/null
+++ b/pycontrails/utils/dependencies.py
@@ -0,0 +1,62 @@
+"""Raise ``ModuleNotFoundError`` when dependencies are not met."""
+
+from typing import NoReturn
+
+
+def raise_module_not_found_error(
+    name: str,
+    package_name: str,
+    module_not_found_error: ModuleNotFoundError,
+    pycontrails_optional_package: str | None = None,
+    extra: str | None = None,
+) -> NoReturn:
+    """Raise ``ModuleNotFoundError`` with a helpful message.
+
+    Parameters
+    ----------
+    name : str
+        The name describing the context of the ``ModuleNotFoundError``. For example,
+        if the module is required for a specific function, the name could be
+        "my_function function". If the module is required for a specific method,
+        the name could be "MyClass.my_method method". If the module is required
+        for an entire pycontrails module, the name could be "my_module module".
+    package_name : str
+        The name of the package that is required. This should be the full name of
+        the python package, which may be different from the name of the module
+        that is actually imported. For example, if ``import sklearn`` triggers
+        the ``ModuleNotFoundError``, the ``package_name`` should be "scikit-learn".
+    module_not_found_error : ModuleNotFoundError
+        The ``ModuleNotFoundError`` that was raised. This is simply passed to the
+        ``from`` clause of the ``raise`` statement below.
+    pycontrails_optional_package : str, optional
+        The name of the optional pycontrails package that can be used to
+        install the required package. See the ``pyproject.toml`` file.
+    extra : str, optional
+        Any extra information that should be included in the error message.
+        This is appended to the end of the error message.
+    """
+    # Put the function or method or module name in quotes if the full name
+    # contains a space.
+    try:
+        n1, n2 = name.split(" ")
+    except ValueError:
+        if "'" not in name:
+            name = f"'{name}'"
+    else:
+        if "'" not in n1:
+            n1 = f"'{n1}'"
+        name = f"{n1} {n2}"
+
+    msg = (
+        f"The {name} requires the '{package_name}' package. "
+        f"This can be installed with 'pip install {package_name}'"
+    )
+    if pycontrails_optional_package:
+        msg = f"{msg} or 'pip install pycontrails[{pycontrails_optional_package}]'."
+    else:
+        msg = f"{msg}."
+
+    if extra:
+        msg = f"{msg} {extra}"
+
+    raise ModuleNotFoundError(msg) from module_not_found_error