In my docker image which uses PHP 7.1 w/ a 2.1.0 compatible GD, I am able to run the scheduled report tests that generate images w/o issue (and they generate the same results as on travis). So I think the check for PHP 5.6 here might not be needed.
Could someone confirm? If it's really not needed, removing the line would make it a little bit easier for me to run them locally.
Just tested that with my PHP 7.1.3 and GD 2.1.1. While PDF tests work fine, the HTML reports fail with changed images. Maybe it would work with GD 2.1.0, but don't have enough time to set up an instance with that specific version right now
I tested this as well and it's strange it works sometimes and sometimes not... anyway it's not super important, so I'm going to close this.