The following program will segfault the interpreter:

#include <Python.h>
int main() {
    Py_Initialize();
    PyRun_SimpleString("import unittest");
    Py_Finalize();

    Py_Initialize();
    PyRun_SimpleString("import unittest");  /* segfault here */
    Py_Finalize();
}

This only seems to happen with the unittest module. This is something that used to work but broke somewhere between python 3.7 and 3.8.

The code above can also be found on github as a cmake project for your convenience:
https://github.com/TheComet/python3.8-unittest-broken