git-cl: Only display a detailed message when git-cl fails.
git-cl: Only display a detailed message when git-cl fails.

git-cl will print the path to the collected traces and git info,
but will only display the detailed message when git-cl fails.

Bug: 961663, 955206
Change-Id: I0a4d470aba24d696bdd5e02e069833f47cf56c02
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1615665
Commit-Queue: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Reviewed-by: Dirk Pranke <6693ee08b084bb2ffa767f664c99b689395e0e4b@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools