bot_update: ensure correct depot_tools checkout is used.

recipe_modules/bot_update/api.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.
 
 
 """Recipe module to ensure a checkout is consistant on a bot."""
 
 from recipe_engine import recipe_api
 
 
@@ skipping 16 matching lines @@
     super(BotUpdateApi, self).__init__(*args, **kwargs)
 
   def __call__(self, name, cmd, **kwargs):
     """Wrapper for easy calling of bot_update."""
     assert isinstance(cmd, (list, tuple))
     bot_update_path = self.resource('bot_update.py')
     kwargs.setdefault('infra_step', True)
     kwargs.setdefault('env', {})
     kwargs['env'].setdefault('PATH', '%(PATH)s')
     kwargs['env']['PATH'] = self.m.path.pathsep.join([
-        kwargs['env']['PATH'], str(self._module.PACKAGE_REPO_ROOT)])
+        str(self._module.PACKAGE_REPO_ROOT), kwargs['env']['PATH']])

[iannucci, 2016/09/16 07:25:59]

aarrrrggghhhh :'(

This explains so much :(

     return self.m.python(name, bot_update_path, cmd, **kwargs)
 
   @property
   def last_returned_properties(self):
       return self._last_returned_properties
 
   # DO NOT USE.
   # The below method will be removed after there are no more callers of
   # tryserver.maybe_apply_issue (skbug.com/5588).
   def apply_gerrit_ref(self, root, gerrit_no_reset=False,
@@ skipping 235 matching lines @@
 
         # bot_update actually just sets root to be the folder name of the
         # first solution.
         if step_result.json.output['did_run']:
           co_root = step_result.json.output['root']
           cwd = kwargs.get('cwd', self.m.path['slave_build'])
           if 'checkout' not in self.m.path:
             self.m.path['checkout'] = cwd.join(*co_root.split(self.m.path.sep))
 
     return step_result