Handle KeyboardInterrupt consistently in python scripts

git_new_branch.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 import argparse
 import sys
 
 import subprocess2
 
@@ skipping 30 matching lines @@
       else:
         # TODO(iannucci): Detect unclean workdir then stash+pop if we need to
         # teleport to a conflicting portion of history?
         run('checkout', '--track', opts.upstream, '-b', opts.branch_name)
     get_or_create_merge_base(opts.branch_name)
   except subprocess2.CalledProcessError as cpe:
     sys.stdout.write(cpe.stdout)
     sys.stderr.write(cpe.stderr)
     return 1
   sys.stderr.write('Switched to branch %s.\n' % opts.branch_name)
+  return 0
 
 
 if __name__ == '__main__':  # pragma: no cover
-  sys.exit(main(sys.argv[1:]))
+  try:
+    sys.exit(main(sys.argv[1:]))
+  except KeyboardInterrupt:
+    sys.stderr.write('interrupted\n')
+    sys.exit(1)