* stable-2.6:
  http/__init__.py: Remove extraneous argument
  rapi.testutils: Add utility to format HTTP headers
  rapi.testutils: Return headers from mock utility
  http: Add wrapper for mimetools.Message
  Add missing tests for commit f0d22861

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>