Better exception messages when we could not find proper executable - c…

…loses #598

newsfragments/598.feature.rst

@@ -0,0 +1 @@
+Add your info here

pytest_postgresql/exceptions.py

@@ -0,0 +1,9 @@
+"""pytest-postgresql's exceptions."""
+
+
+class ExecutableMissingException(FileNotFoundError):
+    """Exception risen when PgConfig was not found."""
+
+
+class PostgreSQLUnsupported(Exception):
+    """Exception raised when unsupported postgresql would be detected."""

pytest_postgresql/executor.py

@@ -30,6 +30,8 @@
 from mirakuru.exceptions import ProcessFinishedWithError
 from pkg_resources import parse_version
 
+from pytest_postgresql.exceptions import ExecutableMissingException, PostgreSQLUnsupported
+
 _LOCALE = "C.UTF-8"
 
 if platform.system() == "Darwin":
@@ -39,10 +41,6 @@
 T = TypeVar("T", bound="PostgreSQLExecutor")
 
 
-class PostgreSQLUnsupported(Exception):
-    """Exception raised when unsupported postgresql would be detected."""
-
-
 class PostgreSQLExecutor(TCPExecutor):
     """PostgreSQL executor running on pg_ctl.
 
@@ -195,7 +193,13 @@ def wait_for_postgres(self) -> None:
     @property
     def version(self) -> Any:
         """Detect postgresql version."""
-        version_string = subprocess.check_output([self.executable, "--version"]).decode("utf-8")
+        try:
+            version_string = subprocess.check_output([self.executable, "--version"]).decode("utf-8")
+        except FileNotFoundError as ex:
+            raise ExecutableMissingException(
+                f"Could not found {self.executable}. Is PostgreSQL server installed? "
+                f"Alternatively pg_config installed might be from different version that postgresql-server."
+            ) from ex
         matches = self.VERSION_RE.search(version_string)
         assert matches is not None
         return parse_version(matches.groupdict()["version"])

pytest_postgresql/factories/process.py

@@ -26,6 +26,7 @@
 from pytest import FixtureRequest, TempPathFactory
 
 from pytest_postgresql.config import get_config
+from pytest_postgresql.exceptions import ExecutableMissingException
 from pytest_postgresql.executor import PostgreSQLExecutor
 from pytest_postgresql.janitor import DatabaseJanitor
 
@@ -95,9 +96,14 @@ def postgresql_proc_fixture(
         # check if that executable exists, as it's no on system PATH
         # only replace if executable isn't passed manually
         if not os.path.exists(postgresql_ctl) and executable is None:
-            pg_bindir = subprocess.check_output(
-                ["pg_config", "--bindir"], universal_newlines=True
-            ).strip()
+            try:
+                pg_bindir = subprocess.check_output(
+                    ["pg_config", "--bindir"], universal_newlines=True
+                ).strip()
+            except FileNotFoundError as ex:
+                raise ExecutableMissingException(
+                    "Could not found pg_config executable. Is it in systenm $PATH?"
+                ) from ex
             postgresql_ctl = os.path.join(pg_bindir, "pg_ctl")
 
         tmpdir = tmp_path_factory.mktemp(f"pytest-postgresql-{request.fixturename}")

tests/test_executor.py

@@ -10,7 +10,8 @@
 from pytest import FixtureRequest
 
 from pytest_postgresql.config import get_config
-from pytest_postgresql.executor import PostgreSQLExecutor, PostgreSQLUnsupported
+from pytest_postgresql.exceptions import PostgreSQLUnsupported
+from pytest_postgresql.executor import PostgreSQLExecutor
 from pytest_postgresql.factories import postgresql, postgresql_proc
 from pytest_postgresql.retry import retry