https://github.com/wikimedia/mediawiki-libs-etcd/blob/master/.travis.yml#L11
test/phpunit.xml doesn't exist, so script: phpunit -c test/phpunit.xml failes in .travis.yml
There is a phpunit.xml.dist in the root though
https://github.com/wikimedia/mediawiki-libs-etcd/runs/62055361
https://travis-ci.com/wikimedia/mediawiki-libs-etcd/jobs/177007399
$ phpunit -c test/phpunit.xml Could not read "test/phpunit.xml". The command "phpunit -c test/phpunit.xml" exited with 1.