Improve diagnostic message for wrong gclient config

gclient_scm.py

 # Copyright (c) 2012 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.
 
 """Gclient-specific SCM-specific operations."""
 
 from __future__ import print_function
 
 import errno
 import logging
@@ skipping 155 matching lines @@
     return getattr(self, command)(options, args, file_list)
 
   @staticmethod
   def _get_first_remote_url(checkout_path):
     log = scm.GIT.Capture(
         ['config', '--local', '--get-regexp', r'remote.*.url'],
         cwd=checkout_path)
     # Get the second token of the first line of the log.
     return log.splitlines()[0].split(' ', 1)[1]
 
+  def GetCacheMirror(self):
+    if (getattr(self, 'cache_dir', None)):
+      url, _ = gclient_utils.SplitUrlRevision(self.url)
+      return git_cache.Mirror(url)
+    return None
+
   def GetActualRemoteURL(self, options):
     """Attempt to determine the remote URL for this SCMWrapper."""
     # Git
     if os.path.exists(os.path.join(self.checkout_path, '.git')):
       actual_remote_url = self._get_first_remote_url(self.checkout_path)
 
-      # If a cache_dir is used, obtain the actual remote URL from the cache.
-      if getattr(self, 'cache_dir', None):
-        url, _ = gclient_utils.SplitUrlRevision(self.url)
-        mirror = git_cache.Mirror(url)
-        if (mirror.exists() and mirror.mirror_path.replace('\\', '/') ==
-            actual_remote_url.replace('\\', '/')):
-          actual_remote_url = self._get_first_remote_url(mirror.mirror_path)
+      mirror = self.GetCacheMirror()
+      # If the cache is used, obtain the actual remote URL from there.
+      if (mirror and mirror.exists() and
+          mirror.mirror_path.replace('\\', '/') ==
+          actual_remote_url.replace('\\', '/')):
+        actual_remote_url = self._get_first_remote_url(mirror.mirror_path)
       return actual_remote_url
 
     # Svn
     if os.path.exists(os.path.join(self.checkout_path, '.svn')):
       return scm.SVN.CaptureLocalInfo([], self.checkout_path)['URL']
     return None
 
   def DoesRemoteURLMatch(self, options):
     """Determine whether the remote URL of this checkout is the expected URL."""
     if not os.path.exists(self.checkout_path):
@@ skipping 1514 matching lines @@
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'theirs-conflict'))
     elif options.manually_grab_svn_rev:
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'postpone'))
     elif command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
       new_command.extend(('--accept', 'postpone'))
     return new_command