minor tidy of cirrus and nox

.cirrus.yml

@@ -3,16 +3,14 @@
 #   - https://cirrus-ci.org/guide/writing-tasks/#environment-variables
 #   - https://cirrus-ci.org/guide/tips-and-tricks/#sharing-configuration-between-tasks
 #   - https://cirrus-ci.org/guide/linux/
-#   - https://cirrus-ci.org/guide/macOS/
-#   - https://cirrus-ci.org/guide/windows/
 #   - https://hub.docker.com/_/gcc/
 #   - https://hub.docker.com/_/python/
 
 #
 # Global defaults.
 #
 container:
-  image: python:3.8
+  image: gcc:latest
   cpu: 2
   memory: 4G
 
@@ -84,6 +82,7 @@ linux_task_template: &LINUX_TASK_TEMPLATE
       - echo "${CIRRUS_TASK_NAME}"
       - echo "${NOX_CACHE_BUILD}"
 
+
 #
 # YAML alias for compute credits.
 #
@@ -113,6 +112,10 @@ lint_task:
   only_if: ${SKIP_LINT_TASK} == ""
   << : *CREDITS_TEMPLATE
   auto_cancellation: true
+  container:
+    image: python:3.8
+    cpu: 2
+    memory: 4G
   name: "${CIRRUS_OS}: flake8 and black"
   pip_cache:
     folder: ~/.cache/pip
@@ -141,10 +144,6 @@ test_minimal_task:
     env:
       PY_VER: 3.8
   name: "${CIRRUS_OS}: py${PY_VER} tests (minimal)"
-  container:
-    image: gcc:latest
-    cpu: 2
-    memory: 4G
   << : *LINUX_TASK_TEMPLATE
   tests_script:
     - export CONDA_OVERRIDE_LINUX="$(uname -r | cut -d'+' -f1)"
@@ -187,14 +186,9 @@ test_full_task:
 gallery_task:
   only_if: ${SKIP_GALLERY_TASK} == "" && ${SKIP_ALL_DOC_TASKS} == ""
   << : *CREDITS_TEMPLATE
-  matrix:
-    env:
-      PY_VER: 3.8
+  env:
+    PY_VER: 3.8
   name: "${CIRRUS_OS}: py${PY_VER} doc tests (gallery)"
-  container:
-    image: gcc:latest
-    cpu: 2
-    memory: 4G
   << : *IRIS_TEST_DATA_TEMPLATE
   << : *LINUX_TASK_TEMPLATE
   tests_script:
@@ -211,17 +205,11 @@ gallery_task:
 doctest_task:
   only_if: ${SKIP_DOCTEST_TASK} == "" && ${SKIP_ALL_DOC_TASKS} == ""
   << : *CREDITS_TEMPLATE
-  matrix:
-    env:
-      PY_VER: 3.8
-  name: "${CIRRUS_OS}: py${PY_VER} doc tests"
-  container:
-    image: gcc:latest
-    cpu: 2
-    memory: 4G
   env:
+    PY_VER: 3.8
     MPL_RC_DIR: ${HOME}/.config/matplotlib
     MPL_RC_FILE: ${HOME}/.config/matplotlib/matplotlibrc
+  name: "${CIRRUS_OS}: py${PY_VER} doc tests"
   << : *IRIS_TEST_DATA_TEMPLATE
   << : *LINUX_TASK_TEMPLATE
   tests_script:
@@ -241,17 +229,11 @@ doctest_task:
 linkcheck_task:
   only_if: ${SKIP_LINKCHECK_TASK} == "" && ${SKIP_ALL_DOC_TASKS} == ""
   << : *CREDITS_TEMPLATE
-  matrix:
-    env:
-      PY_VER: 3.8
-  name: "${CIRRUS_OS}: py${PY_VER} doc link check"
-  container:
-    image: gcc:latest
-    cpu: 2
-    memory: 4G
   env:
+    PY_VER: 3.8
     MPL_RC_DIR: ${HOME}/.config/matplotlib
     MPL_RC_FILE: ${HOME}/.config/matplotlib/matplotlibrc
+  name: "${CIRRUS_OS}: py${PY_VER} doc link check"
   << : *LINUX_TASK_TEMPLATE
   tests_script:
     - export CONDA_OVERRIDE_LINUX="$(uname -r | cut -d'+' -f1)"

noxfile.py

@@ -50,16 +50,16 @@ def venv_populated(session: nox.sessions.Session) -> bool:
 def venv_changed(session: nox.sessions.Session) -> bool:
     """Returns True if the installed session is different to that specified
     in the lockfile."""
+    changed = False
     cache = session_cachefile(session)
     lockfile = session_lockfile(session)
     if cache.is_file():
         with open(lockfile, "rb") as fi:
             expected = hashlib.sha256(fi.read()).hexdigest()
         with open(cache, "r") as fi:
             actual = fi.read()
-        return actual != expected
-    else:
-        return False
+        changed = actual != expected
+    return changed
 
 
 def cache_venv(session: nox.sessions.Session) -> None:
@@ -140,7 +140,7 @@ def prepare_venv(session: nox.sessions.Session) -> None:
         session.virtualenv.reuse_existing = _re_orig
         cache_venv(session)
 
-    logger.debug(f"Environment {venv_dir} up to date")
+    logger.debug(f"Environment {venv_dir} is up to date")
 
     cache_cartopy(session)
 
@@ -210,7 +210,6 @@ def tests(session: nox.sessions.Session):
     """
     prepare_venv(session)
     session.install("--no-deps", "--editable", ".")
-
     session.run(
         "python",
         "-m",