Print nice error in url error.

gclient_scm.py

 # Copyright 2009 Google Inc.  All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #      http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 150 matching lines @@
 
     if options.manually_grab_svn_rev:
       # Retrieve the current HEAD version because svn is slow at null updates.
       if not revision:
         from_info_live = CaptureSVNInfo(from_info['URL'], '.')
         revision = int(from_info_live['Revision'])
         rev_str = ' at %d' % revision
 
     if from_info['URL'] != components[0]:
       to_info = CaptureSVNInfo(url, '.')
+      if not to_info.get('Repository Root') or not to_info.get('UUID'):
+        # The url is invalid or the server is not accessible, it's safer to bail
+        # out right now.
+        raise gclient_utils.Error('This url is unreachable: %s' % url)
       can_switch = ((from_info['Repository Root'] != to_info['Repository Root'])
                     and (from_info['UUID'] == to_info['UUID']))
       if can_switch:
         print("\n_____ relocating %s to a new checkout" % self.relpath)
         # We have different roots, so check if we can switch --relocate.
         # Subversion only permits this if the repository UUIDs match.
         # Perform the switch --relocate, then rewrite the from_url
         # to reflect where we "are now."  (This is the same way that
         # Subversion itself handles the metadata when switch --relocate
         # is used.)  This makes the checks below for whether we
@@ skipping 404 matching lines @@
         # Col 3
         if wc_status[0].getAttribute('copied') == 'true':
           statuses[3] = '+'
         # Col 4
         if wc_status[0].getAttribute('switched') == 'true':
           statuses[4] = 'S'
         # TODO(maruel): Col 5 and 6
         item = (''.join(statuses), file)
         results.append(item)
   return results