We currently observe a failing test for Python 3.7 on Linux. I have not been able to reproduce it locally (where I use Anaconda's Python which is compiled with PYMALLOC) yet.

The last working build was https://travis-ci.org/pythonnet/pythonnet/builds/517298836, the first failing one is https://travis-ci.org/pythonnet/pythonnet/jobs/525395893.

Since between those two, only a completely unrelated test was changed as it started to fail with the new Mono version, I guess the new error is due to some package difference between the two builds, maybe Python itself.