buildbucket: put_batch endpoint

appengine/cr-buildbucket/errors.py

 # Copyright 2014 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 re
 
 
 BUCKET_NAME_REGEX = re.compile(r'^[0-9a-z_\.\-/]{1,100}$')
 
 
@@ skipping 19 matching lines @@
 
 class LeaseExpiredError(Error):
   """Raised when provided lease_key does not match the current one."""
 
 
 def validate_bucket_name(bucket):
   """Raises InvalidInputError if bucket name is invalid."""
   if not bucket:
     raise InvalidInputError('Bucket not specified')
   if not isinstance(bucket, basestring):
-    raise InvalidInputError('Bucket must be a string')
+    raise InvalidInputError(
+        'Bucket must be a string. It is %s.' % type(bucket).__name__)
   if not BUCKET_NAME_REGEX.match(bucket):
     raise InvalidInputError(
         'Bucket name "%s" does not match regular expression %s' %
         (bucket, BUCKET_NAME_REGEX.pattern))