[pinpoint] Add QuestGenerator object.

dashboard/dashboard/pinpoint/models/change.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import collections
 
 from dashboard.common import namespaced_stored_object
 from dashboard.services import gitiles_service
 
 
@@ skipping 217 matching lines @@
     # Translate repository if it's a URL.
     repository_from_url = _Repository(repository)
     if repository_from_url:
       repository = repository_from_url
 
     dep = cls(repository, data['git_hash'])
 
     try:
       gitiles_service.CommitInfo(dep.repository_url, dep.git_hash)
     except gitiles_service.NotFoundError as e:
-      raise KeyError(e)
+      raise KeyError(str(e))
 
     return dep
 
   @classmethod
   def Midpoint(cls, dep_a, dep_b):
     """Return a Dep halfway between the two given Deps.
 
     Uses Gitiles to look up the commit range.
 
     Args:
@@ skipping 59 matching lines @@
 
   repositories = namespaced_stored_object.Get(_REPOSITORIES_KEY)
   repository = repository_url.split('/')[-1]
 
   if repository in repositories:
     raise AssertionError("Attempted to add a repository that's already in the "
                          'Datastore: %s: %s' % (repository, repository_url))
 
   repositories[repository] = {'repository_url': repository_url}
   namespaced_stored_object.Set(_REPOSITORIES_KEY, repositories)