Add initial postprocess unit test thingy.

recipe_engine/env.py

 # 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.
 
 """Sets up recipe engine Python environment."""
 
 import contextlib
 import os
 import sys
 
 # Hook up our third party vendored packages.
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 THIRD_PARTY = os.path.join(BASE_DIR, 'recipe_engine', 'third_party')
 
 # Real path manipulation.
 sys.path = [
     os.path.join(THIRD_PARTY),
     os.path.join(THIRD_PARTY, 'requests'),
     os.path.join(THIRD_PARTY, 'six'),
     os.path.join(THIRD_PARTY, 'client-py'),
     os.path.join(THIRD_PARTY, 'mock-1.0.1'),
+    os.path.join(THIRD_PARTY, 'astunparse'),
 ] + sys.path
 
 # Hack up our "pkg_resources" to import our local protobuf instead of the system
 # one.
 #
 # As per https://github.com/google/protobuf/issues/1484:
 # The protobuf library is meant to be installed. It is either a system library
 # or a virtualenv library, but not something you can just point "sys.path" to
 # anymore ... well, not without hacks.
 #
@@ skipping 31 matching lines @@
 
 # From here on out, we're back to normal imports. Let's assert that the we're
 # using the correct protobuf package, though.
 #
 # We use "realpath" here because the importer may resolve the path differently
 # based on symlinks, and we want to make sure our calculated path matches the
 # impoter's path regardless.
 import google.protobuf
 assert (os.path.realpath(THIRD_PARTY) in
         os.path.realpath(google.protobuf.__path__[0]))