I've hit this assert a few times, seeing the output of the set usually
helps highlight quickly how my command-line arguments are broken.

Bug:
Change-Id: I8b80b635df91f2707a599a33ab9b4959b3c76614
Reviewed-on: https://chromium-review.googlesource.com/535834Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>