Since legacy/trac#15344 got implemented the output of the tests is redirected to separate logs and the `test-suite.log` summary file. This makes it hard to find the exact issue when Jenkins is failing (it only shows PASS or FAIL). The [Automake documentation](https://www.gnu.org/software/automake/manual/automake.html#Parallel-Test-Harness) mentions the VERBOSE environment variable which prints the `test-suite.log` file when tests fail.