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
diff --git a/git_new_branch.py b/git_new_branch.py
index 18ce018..03b0fcc 100755
--- a/git_new_branch.py
+++ b/git_new_branch.py
@@ -48,7 +48,12 @@
     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)