These changes are all independent of each other; I just didn’t feel
like making dozens of commits for them.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
This commit adds automatic detection of extra output (other than
printed by testing library or tools) in stderr and stdout by code under
test test-backend when it is run with flag --ban-console-output.
It also prints the test that produced the extra console output.
Fixes: #1587.
Anders Kaseorg
Mohit Gupta