Ensure missing test warning fails on CI.
Summary: Depends on D1075
Test Plan: TEAMCITY_VERSION=1 ./test/functional/test_runner.py
Reviewers: deadalnix, jasonbcox, #bitcoin_abc
Reviewed By: deadalnix, #bitcoin_abc
Subscribers: teamcity
Differential Revision: https://reviews.bitcoinabc.org/D1076