travis based on dist:trusty fails on some workers

[mlechner]

Travis CI is upgrading to use trusty based workers instead of precise. Some workers based on trusty seem to face problems downloading gradle, because they think the cert where gradle...zip is fetched from a url that has a revoked ssl-cert. This results into an error similar to https://github.com/facebook/react-native/issues/14091 As a following, travis builds sometimes fail and sometimes work depending on the worker. As an example compare https://travis-ci.org/OpenBfS/mapfish-print/jobs/265912901 with https://travis-ci.org/mapfish/mapfish-print/jobs/265910777 - same commit same travis.yml, ... once fail, once ok. The problem only occurs when trying to build with openjdk7.

Until this issue with travis trusty workers is fixed, should mp3 fall back to precise by adding a dist:precise to .travis.yml? I could provide a PR if appropriate.

Or is there any other reasonable explanation what happens here?

[pvalsecc]

Is it still the case?