Isolate configuration related code better

- create the global `config` object inside the
  `urban_meal_delivery.configuration` module
- streamline documentation and comments

setup.cfg

@@ -272,4 +272,4 @@ console_output_style = count
 env =
     TESTING=true
 markers =
-    e2e: integration tests, inlc., for example, tests touching a database
+    e2e: integration tests, incl., for example, tests touching the database

src/urban_meal_delivery/__init__.py

@@ -5,11 +5,12 @@ Example:
     >>> umd.__version__ != '0.0.0'
     True
 """
+# The config object must come before all other project-internal imports.
+from urban_meal_delivery.configuration import config  # noqa:F401 isort:skip
 
-import os as _os
 from importlib import metadata as _metadata
 
-from urban_meal_delivery import configuration as _configuration
+from urban_meal_delivery import db  # noqa:F401
 
 
 try:
@@ -24,14 +25,3 @@ else:
     __author__ = _pkg_info['author']
     __pkg_name__ = _pkg_info['name']
     __version__ = _pkg_info['version']
-
-
-# Global `config` object to be used in the package.
-config: _configuration.Config = _configuration.make_config(
-    'testing' if _os.getenv('TESTING') else 'production',
-)
-
-
-# Import `db` down here as it depends on `config`.
-# pylint:disable=wrong-import-position
-from urban_meal_delivery import db  # noqa:E402,F401 isort:skip

src/urban_meal_delivery/configuration.py

@@ -73,7 +73,7 @@ def make_config(env: str = 'production') -> Config:
     """Create a new `Config` object.
 
     Args:
-        env: either 'production' or 'testing'; defaults to the first
+        env: either 'production' or 'testing'
 
     Returns:
         config: a namespace with all configurations
@@ -81,7 +81,8 @@ def make_config(env: str = 'production') -> Config:
     Raises:
         ValueError: if `env` is not as specified
     """  # noqa:DAR203
-    config: Config
+    config: Config  # otherwise mypy is confused
+
     if env.strip().lower() == 'production':
         config = ProductionConfig()
     elif env.strip().lower() == 'testing':
@@ -94,3 +95,6 @@ def make_config(env: str = 'production') -> Config:
         warnings.warn('Bad configurartion: no DATABASE_URI set in the environment')
 
     return config
+
+
+config = make_config('testing' if os.getenv('TESTING') else 'production')

tests/conftest.py

@@ -5,6 +5,8 @@ import os
 from urban_meal_delivery import config
 
 
+# The TESTING environment variable is set
+# in setup.cfg in pytest's config section.
 if not os.getenv('TESTING'):
     raise RuntimeError('Tests must be executed with TESTING set in the environment')