Some weirdo folks have @ in their USER environment variable. Strip it off.

Review URL: http://codereview.chromium.org/2336002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@48582 0039d316-1c4b-4281-b951-d872f2087c98

trychange.py

@@ -602,6 +602,9 @@ def TryChange(argv,
 
   logging.debug(argv)
 
+  # Strip off any @ in the user, otherwise svn gets confused.
+  options.user = options.user.split('@', 1)[0]
+
   if options.rietveld_url:
     # Try to extract the review number if possible and fix the protocol.
     if not '://' in options.rietveld_url: