GClient should allow having 'url': None in .gclient...

gclient.py

 #!/usr/bin/python
 #
 # Copyright 2008 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
 #
@@ skipping 652 matching lines @@
     # Run on the base solutions first.
     for solution in solutions:
       name = solution["name"]
       deps_file = solution.get("deps_file", self._options.deps_file)
       if '/' in deps_file or '\\' in deps_file:
         raise Error("deps_file name must not be a path, just a filename.")
       if name in entries:
         raise Error("solution %s specified more than once" % name)
       url = solution["url"]
       entries[name] = url
-      if run_scm:
+      if run_scm and url:
         self._options.revision = revision_overrides.get(name)
         scm = gclient_scm.CreateSCM(url, self._root_dir, name)
         scm.RunCommand(command, self._options, args, file_list)
         file_list = [os.path.join(name, file.strip()) for file in file_list]
         self._options.revision = None
       try:
         deps_content = FileRead(os.path.join(self._root_dir, name,
                                              deps_file))
       except IOError, e:
         if e.errno != errno.ENOENT:
@@ skipping 499 matching lines @@
 
 if "__main__" == __name__:
   try:
     result = Main(sys.argv)
   except Error, e:
     print >> sys.stderr, "Error: %s" % str(e)
     result = 1
   sys.exit(result)
 
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