Added headers and code tags

Made sure that when limiting message size, at least part of the message
is seen.

Change-Id: I404e2f7e86907f701332a62fe46334ff437cca03
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1690741Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Debrian Figueroa <debrian@google.com>