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_rebase_update.py

@@ -187,7 +187,7 @@ def rebase_branch(branch, parent, start_hash):
   return True
 
 
-def main(args=()):
+def main(args=None):
   parser = argparse.ArgumentParser()
   parser.add_argument('--verbose', '-v', action='store_true')
   parser.add_argument('--no_fetch', '--no-fetch', '-n',
@@ -270,4 +270,8 @@ def main(args=()):
 
 
 if __name__ == '__main__':  # pragma: no cover
-  sys.exit(main(sys.argv[1:]))
+  try:
+    sys.exit(main())
+  except KeyboardInterrupt:
+    sys.stderr.write('interrupted\n')
+    sys.exit(1)