Travis CI tests fail when dist: xenial is used instead of dist: trusty

Why does __git.test.test_remote.TestRemote__ fail in all versions of Python on Travis CI when __dist: xenial__ is used instead of the Travis CI default of __dist: trusty__?  For Python >= 3.7 it is required that Travis runs on Xenial: https://github.com/gitpython-developers/GitPython/blob/master/.travis.yml#L11-L14

https://travis-ci.org/gitpython-developers/GitPython/builds/481862926