Vendor virtualenv, update to 15.1.0.

bootstrap/update_vendoring.py

 #!/usr/bin/env python
 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Regenerates vendored components and derivative files from external sources.
 
 This is a utililty script that is intended to be run on a Linux-based system.
 Other operating systems may work, but are not supported.
 
@@ skipping 259 matching lines @@
 
       d = _path(REPO_DIR, d)
       all_proto = glob.glob(os.path.join(d, '*.proto'))
 
       c.check_call([c.tool('protoc'), '-I', d, '--python_out', outdir] +
                     all_proto)
 
 
 _ACTIONS = (
     _VendoredPipPackage(
+        'bootstrap/virtualenv',
+        name='virtualenv',
+        version='15.1.0'),
+    )
+
+    _VendoredPipPackage(
         'recipe_engine/third_party/six',
         name='six',
         version='1.10.0'),
 
     _VendoredPipPackage(
         'recipe_engine/third_party/requests',
         name='requests',
         version='2.10.0'),
 
     _VendoredGitRepo(
@@ skipping 47 matching lines @@
       vdir = os.path.join(td, 'vendor_%d' % (i,))
       os.makedirs(vdir)
 
       # Execute the vendor script.
       act.run(c, vdir, opts)
 
 
 if __name__ == '__main__':
   logging.basicConfig(level=logging.DEBUG)
   sys.exit(main(sys.argv[1:]))