Catch an error when trying to generate an access token.

endpoints/index.py

@@ -33,10 +33,14 @@ def generate_headers(role='read'):
 
       if has_token_request:
         repo = model.get_repository(namespace, repository)
+        if repo:
           token = model.create_access_token(repo, role)
           token_str = 'signature=%s' % token.code
           response.headers['WWW-Authenticate'] = token_str
           response.headers['X-Docker-Token'] = token_str
+        else:
+          logger.info('Token request in non-existing repo: %s/%s' %
+                      (namespace, repository))
 
       return response
     return wrapper