Return default value for pkg_version if missing

Particularly when writing test code the project as defined by your
oslo.config may not exist. In which case we should just use some default
value (in this case "unknown") for the version string rather than fail
to load.

Change-Id: I176fced85468683268e35ce81e63baa17f0e6b84
Closes-Bug: #1494138

keystonemiddleware/auth_token/__init__.py

@@ -427,7 +427,10 @@ def _conf_values_type_convert(conf):
 
 
 def _get_project_version(project):
-    return pkg_resources.get_distribution(project).version
+    try:
+        return pkg_resources.get_distribution(project).version
+    except pkg_resources.DistributionNotFound:
+        return "unknown"
 
 
 def _uncompress_pkiz(token):

keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py

@@ -15,6 +15,7 @@
 import datetime
 import logging
 import os
+import pkg_resources
 import shutil
 import stat
 import tempfile
@@ -2474,6 +2475,19 @@ class TestAuthPluginUserAgentGeneration(BaseAuthTokenMiddlewareTest):
         project_with_version = '{0}/{1} '.format(project, project_version)
         self._assert_user_agent(app, project_with_version, project_version)
 
+    def test_project_not_installed_results_in_unknown_version(self):
+        project = uuid.uuid4().hex
+
+        conf = {'username': self.username,
+                'auth_url': self.auth_url,
+                'project': project}
+
+        v = pkg_resources.get_distribution('keystonemiddleware').version
+
+        app = self.create_simple_middleware(conf=conf, use_global_conf=True)
+        project_with_version = '{0}/{1} '.format(project, 'unknown')
+        self._assert_user_agent(app, project_with_version, v)
+
     def test_project_in_oslo_configuration(self):
         project = uuid.uuid4().hex
         project_version = uuid.uuid4().hex