Add gvacommon.settings_utils

This commit adds a get_env_variable function that is taken from gva's
settings.base module into a new module gvacommon.settings_utils.

gvacommon/settings_utils.py

@@ -0,0 +1,38 @@
+#
+# gvacommon - common parts of gnuviechadmin
+# Copyright (C) 2016  Jan Dittberner
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+from os import environ
+# Normally you should not import ANYTHING from Django directly
+# into your settings, but ImproperlyConfigured is an exception.
+from django.core.exceptions import ImproperlyConfigured
+
+
+def get_env_variable(var_name):
+    """
+    Get a setting from an environment variable.
+
+    :param str var_name: variable name
+    :raises ImproperlyConfigured: if the environment setting is not defined
+    :return: environment setting value
+    :rtype: str
+    """
+    try:
+        return environ[var_name]
+    except KeyError:
+        error_msg = "Set the %s environment variable" % var_name
+        raise ImproperlyConfigured(error_msg)

gvacommon/tests/test_settings_utils.py

@@ -0,0 +1,40 @@
+# -*- coding: utf-8 -*-
+#
+# gvacommon - common parts of gnuviechadmin
+# Copyright (C) 2016  Jan Dittberner
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+import os
+from unittest import TestCase
+
+from django.core.exceptions import ImproperlyConfigured
+
+from gvacommon.settings_utils import get_env_variable
+
+
+class GetEnvVariableTest(TestCase):
+
+    def test_get_existing_env_variable(self):
+        os.environ['testvariable'] = 'myvalue'
+        self.assertEqual(get_env_variable('testvariable'), 'myvalue')
+
+    def test_get_missing_env_variable(self):
+        if 'missingvariable' in os.environ:
+            del os.environ['missingvariable']
+        with self.assertRaises(ImproperlyConfigured) as e:
+            get_env_variable('missingvariable')
+        self.assertEqual(
+            str(e.exception), 'Set the missingvariable environment variable')
+