Fix versionchecker script

tools/bots/version_checker.py

 #!/usr/bin/python
 
 # Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import json
 import re
 import sys
 
 import bot
 import bot_utils
 
 utils = bot_utils.GetUtils()
 
-VERSION_BUILDER = r'version-checker'
+VERSION_BUILDER = r'versionchecker'
 
 def VersionConfig(name, is_buildbot):
   version_pattern = re.match(VERSION_BUILDER, name)
   if not version_pattern:
       return None
   # We don't really use this, but we create it anyway to use the standard
   # bot execution model.
   return bot.BuildInfo('none', 'none', 'release', 'linux')
 
 def GetLatestVersionFromGCS(channel):
@@ skipping 49 matching lines @@
       print 'Version currently building: %s' % version
       if not ValidateChannelVersion(latest_version, channel):
         print "Validation failed"
         sys.exit(1)
       else:
         print 'Version file changed, sanity checks passed'
 
 if __name__ == '__main__':
   # We pass in None for build_step to avoid building.
   bot.RunBot(VersionConfig, VersionSteps, build_step=None)