Make ConfigInvalid generic

The ConfigInvalid class is now used not only by basicauth middleware
but also by healthcheck middleware. Move it out from basicauth
middleware to a common place.

This change also address a few follow-up items of [1].

[1] 01cd608104

Change-Id: I1865cbfe6ff22ffb7db57cf685e340de4a3568d4

oslo_middleware/basic_auth.py

@@ -22,6 +22,7 @@ import webob
 
 from oslo_config import cfg
 from oslo_middleware import base
+from oslo_middleware import exceptions
 
 LOG = logging.getLogger(__name__)
 
@@ -34,12 +35,6 @@ OPTS = [
 cfg.CONF.register_opts(OPTS, group='oslo_middleware')
 
 
-class ConfigInvalid(Exception):
-    def __init__(self, error_msg):
-        super().__init__(
-            'Invalid configuration file. %(error_msg)s')
-
-
 class BasicAuthMiddleware(base.ConfigurableMiddleware):
     """Middleware which performs HTTP basic authentication on requests"""
 
@@ -135,7 +130,8 @@ def validate_auth_file(auth_file):
                 if entry and ':' in entry:
                     parse_entry(entry)
     except OSError:
-        raise ConfigInvalid(error_msg='Problem reading auth user file')
+        raise exceptions.ConfigInvalid(
+            error_msg='Problem reading auth user file')
 
 
 def parse_entry(entry):

oslo_middleware/exceptions.py

@@ -0,0 +1,17 @@
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+class ConfigInvalid(Exception):
+    def __init__(self, error_msg):
+        super().__init__(
+            'Invalid configuration. %(error_msg)s')

oslo_middleware/healthcheck/__init__.py

@@ -39,7 +39,7 @@ except ImportError:
     greenlet = None
 
 from oslo_middleware import base
-from oslo_middleware.basic_auth import ConfigInvalid
+from oslo_middleware.exceptions import ConfigInvalid
 from oslo_middleware.healthcheck import opts
 
 
@@ -422,13 +422,12 @@ Reason
 
     def _verify_configured_plugins(self):
         backends = self._conf_get('backends')
-        desired_plugins = ['disable_by_file', 'enable_by_files']
+        exclusive_plugins = ['disable_by_file', 'enable_by_files']
-
-        if set(desired_plugins).issubset(set(backends)):
-            raise ConfigInvalid('`enable_by_files` and `disable_by_file`'
-                                ' healthcheck middleware should not be '
-                                'configured at once.')
 
+        if set(exclusive_plugins).issubset(set(backends)):
+            raise ConfigInvalid('`enable_by_files` plugin and '
+                                '`disable_by_file` plugin should not be '
+                                'enabled at the same time.')
 
     def _conf_get(self, key, group='healthcheck'):
         return super(Healthcheck, self)._conf_get(key, group=group)

oslo_middleware/tests/test_auth_basic.py

@@ -21,6 +21,7 @@ from oslo_config import cfg
 import webob
 
 from oslo_middleware import basic_auth as auth
+from oslo_middleware import exceptions as exc
 from oslotest import base as test_base
 
 
@@ -116,7 +117,7 @@ class TestAuthBasic(test_base.BaseTestCase):
         auth.validate_auth_file(auth_file)
         # failed, missing auth file
         auth_file = auth_file + '.missing'
-        self.assertRaises(auth.ConfigInvalid,
+        self.assertRaises(exc.ConfigInvalid,
                           auth.validate_auth_file, auth_file)
         # failed, invalid entry
         auth_file = self.write_auth_file(

oslo_middleware/tests/test_healthcheck.py

@@ -24,7 +24,7 @@ import requests
 import webob.dec
 import webob.exc
 
-from oslo_middleware.basic_auth import ConfigInvalid
+from oslo_middleware.exceptions import ConfigInvalid
 from oslo_middleware import healthcheck
 from oslo_middleware.healthcheck import __main__