bot_update (+recipe_module): treat patch download as infra failure.

scripts/slave/recipe_modules/bot_update/test_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.
 
 import hashlib
 import os
 import struct
 import sys
 
 sys.path.append(
@@ skipping 54 matching lines @@
               'repository': 'https://fake.org/%s.git' % project_name,
               'revision': self.gen_revision(project_name, git_mode),
             }
             for project_name in revision_mapping
           }
         })
 
       if fail_patch:
         output['log_lines'] = [('patch error', 'Patch failed to apply'),]
         output['patch_failure'] = True
+        output['patch_apply_return_code'] = 1
+        if fail_patch == 'download':
+          output['patch_apply_return_code'] = 3
     return self.m.json.output(output)
 
   @staticmethod
   def gen_revision(project, GIT_MODE):
     """Hash project to bogus deterministic revision values."""
     h = hashlib.sha1(project)
     if GIT_MODE:
       return h.hexdigest()
     else:
       return struct.unpack('!I', h.digest()[:4])[0] % 300000