PasteConfigNotFound also raised when keystone.conf not found

Although keystone is looking for paste configuration on startup, this
exception can also be raised when keystone attempts to look in the
regular keystone.conf file for paste configuration, and can't find that
file either. The solution here is just to make the exception slightly
more generic (ConfigFileNotFound), along with it's rendered error
message and improve surrounding comments to better explain the scenario.

Change-Id: I88f1d987113884097b1cdf8c120613613abfb8c9
Closes-Bug: 1254036

keystone/config.py

@@ -30,16 +30,20 @@ configure = config.configure
 
 
 def find_paste_config():
-    """Selects Keystone paste.deploy configuration file.
+    """Find Keystone's paste.deploy configuration file.
+
+    Keystone's paste.deploy configuration file is specified in the
+    ``[paste_deploy]`` section of the main Keystone configuration file,
+    ``keystone.conf``.
+
+    For example::
 
-    Keystone paste.deploy configuration file is selectd in [paste_deploy]
-    section of the main Keystone configuration file.
-    For example:
         [paste_deploy]
         config_file = keystone-paste.ini
 
     :returns: The selected configuration filename
-    :raises: exception.PasteConfigNotFound
+    :raises: exception.ConfigFileNotFound
+
     """
     if CONF.paste_deploy.config_file:
         paste_config = CONF.paste_deploy.config_file
@@ -50,8 +54,11 @@ def find_paste_config():
         paste_config = CONF.config_file[0]
         paste_config_value = paste_config
     else:
+        # this provides backwards compatibility for keystone.conf files that
+        # still have the entire paste configuration included, rather than just
+        # a [paste_deploy] configuration section referring to an external file
         paste_config = CONF.find_file('keystone.conf')
         paste_config_value = 'keystone.conf'
     if not paste_config or not os.path.exists(paste_config):
-        raise exception.PasteConfigNotFound(config_file=paste_config_value)
+        raise exception.ConfigFileNotFound(config_file=paste_config_value)
     return paste_config

keystone/exception.py

@@ -241,6 +241,6 @@ class NotImplemented(Error):
     title = 'Not Implemented'
 
 
-class PasteConfigNotFound(UnexpectedError):
-    message_format = _("The Keystone paste configuration file"
-                       " %(config_file)s could not be found.")
+class ConfigFileNotFound(UnexpectedError):
+    message_format = _("The Keystone configuration file %(config_file)s could "
+                       "not be found.")

keystone/tests/test_config.py

@@ -14,6 +14,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import uuid
+
 from keystone import config
 from keystone import exception
 from keystone import tests
@@ -26,8 +28,8 @@ class ConfigTestCase(tests.TestCase):
     def test_paste_config(self):
         self.assertEqual(config.find_paste_config(),
                          tests.etcdir('keystone-paste.ini'))
-        self.opt_in_group('paste_deploy', config_file='XYZ')
-        self.assertRaises(exception.PasteConfigNotFound,
+        self.opt_in_group('paste_deploy', config_file=uuid.uuid4().hex)
+        self.assertRaises(exception.ConfigFileNotFound,
                           config.find_paste_config)
         self.opt_in_group('paste_deploy', config_file='')
         self.assertEqual(config.find_paste_config(),