Not outputting a newline when not prompting causes the command prompt to
not appear on a new line.

Change-Id: I791c829e1e0b37c9ad5d6bfdb246db4c779be020
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2380598
Auto-Submit: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>