Revert of Removed virtualenv from depot_tools

third_party/cq_client/validate_config.py

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """CQ config validation library."""
 
 import argparse
-# This file was originally copied together with the cq_client library from the
-# internal commit_queue repository and then modified to import protobuf26
-# instead of google.protobuf to prevent conflicts with a different version of
-# google.protobuf that some users of depot_tools have installed. If you need to
-# update this file, please make similar changes again and add this comment back.
-# More details on why we chose to rename the package can be found in the file
-# depot_tools/third_party/protobuf26/README.chromium.
-import protobuf26 as protobuf
+from google import protobuf
 import logging
 import re
 import sys
 
 from cq_client import cq_pb2
 
 
 REQUIRED_FIELDS = [
   'version',
   'rietveld',
@@ skipping 79 matching lines @@
     try:
       re.compile(base)
     except re.error:
       logging.error('failed to parse "%s" in project_bases as a regexp', base)
       return False
 
   # TODO(sergiyb): For each field, check valid values depending on its
   # semantics, e.g. email addresses, regular expressions etc.
 
   return True