chromite_wrapper: add python3 support for except

I don't have an account on the chrome gerrit or whatever, and don't
really want to create one for a oneline patch, so I was hoping you'd be
ok with passing this along through the proper channels.

R=ehmaldonado@chromium.org
Signed-off-by: Marty E. Plummer <hanetzer@startmail.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Bug: None
Change-Id: I3daf58ee802e7c9b144227999f1832b364c5759a
Reviewed-on: https://chromium-review.googlesource.com/1096128Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

support/chromite_wrapper

@@ -69,7 +69,7 @@ def main():
   path = os.path.join(chromite_dir, 'bin', target)
   try:
     os.execv(path, [path] + sys.argv[1:])
-  except EnvironmentError, e:
+  except EnvironmentError as e:
     if e.errno not in (errno.ENOENT, errno.EPERM):
       raise