Update dartfmt message to be less confusing

git_cl.py

 #!/usr/bin/env python
 # 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.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
 from distutils.version import LooseVersion
@@ skipping 3551 matching lines @@
     try:
       command = [dart_format.FindDartFmtToolInChromiumTree()]
       if not opts.dry_run and not opts.diff:
         command.append('-w')
       command.extend(dart_diff_output.splitlines())
 
       stdout = RunCommand(command, cwd=top_dir, env=env)
       if opts.dry_run and stdout:
         return_value = 2
     except dart_format.NotFoundError as e:
-      print ('Unable to check dart code formatting. Dart SDK is not in ' +
-             'this checkout.')
+      print ('Warning: Unable to check Dart code formatting. Dart SDK not ' +
+             'found in this checkout. Files in other languages are still ' +
+             'formatted.')
 
   return return_value
 
 
 @subcommand.usage('<codereview url or issue id>')
 def CMDcheckout(parser, args):
   """Checks out a branch associated with a given Rietveld issue."""
   _, args = parser.parse_args(args)
 
   if len(args) != 1:
@@ skipping 87 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   colorama.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)