Handle KeyboardInterrupt consistently in python scripts

Handle KeyboardInterrupt gracefully rather the printing a
backtrace. Most users of these tools don't expect a
backtrace when then hit Ctrl-C.

Also, fix a few other inconsistencies found in the python
startup code of these different scripts:
- always call main function 'main' (rather than 'Main')
- always return 0 from main function
- if main takes args never include argv[0]

Review URL: https://codereview.chromium.org/955993006

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@294250 0039d316-1c4b-4281-b951-d872f2087c98

git_freezer.py

@@ -22,12 +22,17 @@ def CMDthaw(parser, args):
   return thaw()
 
 
-def main():
+def main(args):
   dispatcher = subcommand.CommandDispatcher(__name__)
-  ret = dispatcher.execute(optparse.OptionParser(), sys.argv[1:])
+  ret = dispatcher.execute(optparse.OptionParser(), args)
   if ret:
     print ret
+  return 0
 
 
 if __name__ == '__main__':
-  main()
+  try:
+    sys.exit(main(sys.argv[1:]))
+  except KeyboardInterrupt:
+    sys.stderr.write('interrupted\n')
+    sys.exit(1)