Remove new lines in TestFail message.

verifier.py has been formatting the test fail message
to include new lines. While that makes the message readable,
the message is cut of at the new line. To display the whole message
we need to remove new lines.

BUG=None.
TEST=Ran test_that <ip> ui_SystemTray. Observed that on failure
test_that outputs the full message that contains the biopic comparison link.

Change-Id: I15c1a8fe34e35c4f743c6d4ab9023abda2c6c560
Reviewed-on: https://chromium-review.googlesource.com/228901
Reviewed-by: David Haddock <dhaddock@chromium.org>
Reviewed-by: Kris Rambish <krisr@chromium.org>
Tested-by: Mussa Kiroga <mussa@chromium.org>
Commit-Queue: Mussa Kiroga <mussa@chromium.org>
1 file changed