MDL-65249, a new redis-related test was added to verify that, after failing to connect to redis a number of times, the behavior was the expected.
And it works like a charm!
But, suddenly, we started to get failures with ALL the travis phpunit runs using php71. Example: https://travis-ci.org/stronk7/moodle/builds/552372633
Only with travis, and only with php71. Both locally and also CI servers are passing the tests with php71 without any problem.
So, the only difference, so far, is that the php version of travis, by default (the one coming within their images) uses to be a little bit old. Right now it's exactly 7.1.11.
And, forcing it to be the current 7.1.30, the tests are back to pass: See https://travis-ci.org/stronk7/moodle/builds/553224011
So this issue is about to update all the supported branches where we are performing php71 phpunit runs (min/max strategy) and force them to use the, verified to pass, php 7.1.30.
Note that I've not been trying different versions, neither looked for an issue @ php or redis bug systems. Just tried current 7.1.30, it worked, so good enough.