Add check to ensure all patches are contributions

This essentially just checks that commit messages do not contain the
string 'not a contribution' as such patches cannot be accepted into
Chromium OS.

TEST=This commit message fails to upload.

Change-Id: Ica5e48dde7320a5a2e7c0bd234fbc98f57e90d49
Commit-Ready: Bernie Thompson <>
Tested-by: Bernie Thompson <>
Reviewed-by: Mike Frysinger <>
2 files changed