I'm not using astroid directly, but discovered this issue downstream using sphinx-autoapi.
It seems I've run into an edge case with partial and the pickle module. I've added a new test case to astroid to showcase my problem: master...renefritze:conditional_test_pickle

With the last commit on that branch the test suite succeeds: https://travis-ci.com/github/renefritze/astroid/jobs/487475875
Dropping the last commit, the suite fails: https://travis-ci.com/github/renefritze/astroid/jobs/487452325
The difference being 307f3ac