GitLab

The syntax for raising a custom exception with all three args is
different between Python 2 & Python 3 to the point where we can't
even do it inline because an incompatible version throws syntax
errors during parsing.  Utilize six's reraise helper for it.

Bug: 983071
Test: `./grit/test_suite_all.py` passes
Change-Id: I2489dfe588c4c650661ece327c5d86e8754269ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1700504Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686221}