The Matplotlib (https://github.com/matplotlib/matplotlib) test suite is seeing errors like

SystemError: 'finally' pops bad exception

We see these both on travis (https://travis-ci.org/matplotlib/matplotlib/jobs/262907186 ) and I can reproduce locally.

Walking the stack in the debugger is all in pytest / py code and in the code path that handles exceptions.

Via debugging-write-to-a-file I am pretty sure that all of the matplotlib specific code is through and there is not an exception.

This may be a upstream python bug, but trying here first with the hope you will be able to help get a more minimal example.