fix error message formatting

inventory_provider/__init__.py

@@ -23,7 +23,7 @@ def create_app():
         'environment variables %r must be defined' % required_env_vars
 
     assert os.path.isfile(os.environ['INVENTORY_PROVIDER_CONFIG_FILENAME']), (
-        'config file %r not found %r' %
+        'config file %r not found' %
         os.environ['INVENTORY_PROVIDER_CONFIG_FILENAME'])
 
     from inventory_provider import config