message: add troubleshooting paragraph for failing py_aggregator tests
diff: @@ -155,3 +155,16 @@ to reinstall Python with the `--enable-shared` option:
  Next, run `cargo clean` to remove the old build artifacts. After that, all tests should pass.
  [You can find more information about the solution here.](https://github.com/PyO3/pyo3/issues/742#issuecomment-577332616)
  +
  +**`cargo test` fails with SIGSEGV: invalid memory reference**
  +
  +This is a known issue with `pyo3`: https://github.com/PyO3/pyo3/issues/288
  +
  +__Solution:__
  +
  +Run the tests with:
  +
  +```none
  +cargo test -- --test-threads=1
  +```
  +
  