Bugfix in tools/build.py: Error -> Exception rename

tools/build.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012, 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 optparse
 import os
 import shutil
@@ skipping 171 matching lines @@
     'android_sdk_tools=%s' % android_sdk_platform_tools
     ]
 
   os.environ['GYP_DEFINES'] = ' '.join(gypDefinesList)
 
 
 def Execute(args):
   process = subprocess.Popen(args)
   process.wait()
   if process.returncode != 0:
-    raise Error(args[0] + " failed")
+    raise Exception(args[0] + " failed")
 
 
 def GClientRunHooks():
   Execute(['gclient', 'runhooks'])
 
 
 def RunhooksIfNeeded(host_os, mode, arch, target_os):
   if host_os != 'linux':
     return
   build_root = utils.GetBuildRoot(host_os)
@@ skipping 116 matching lines @@
         process.wait()
         if process.returncode != 0:
           print "BUILD FAILED"
           return 1
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())