Has slightly friendlier error message on permission errors. No other changes.

R=iannucci@chromium.org, tandrii@chromium.org
BUG=1031057

Change-Id: Ie6dd75285bf6125bc76a1d338f956a303b42f825
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1959085
Auto-Submit: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@google.com>
Commit-Queue: Andrii Shyshkalov <tandrii@google.com>