Tests crash on pypy

Here's output from a recent run:

  tox
  shell: /usr/bin/bash -e {0}
  env:
    pythonLocation: /opt/hostedtoolcache/PyPy/3.9.12/x64
    Python_ROOT_DIR: /opt/hostedtoolcache/PyPy/3.9.12/x64
    Python2_ROOT_DIR: /opt/hostedtoolcache/PyPy/3.9.12/x64
    Python3_ROOT_DIR: /opt/hostedtoolcache/PyPy/3.9.12/x64
    PKG_CONFIG_PATH: /opt/hostedtoolcache/PyPy/3.9.12/x64/bin/lib/pkgconfig
python create: /home/runner/work/cmdix/cmdix/.tox/python
python installdeps: pytest >= 6.2.1
python develop-inst: /home/runner/work/cmdix/cmdix
ERROR: invocation failed (exit code -9), logfile: /home/runner/work/cmdix/cmdix/.tox/python/log/python-3.log
================================== log start ===================================

=================================== log end ====================================
___________________________________ summary ____________________________________
ERROR:   python: InvocationError for command /home/runner/work/cmdix/cmdix/.tox/python/bin/python -m pip freeze (exited with code -9 (SIGKILL)) (exited with code -9)

The process doesn't always fail precisely that way. Here's output from an earlier run:

  tox
  shell: /usr/bin/bash -e {0}
  env:
    pythonLocation: /opt/hostedtoolcache/PyPy/3.9.12/x64
    Python_ROOT_DIR: /opt/hostedtoolcache/PyPy/3.9.12/x64
    Python2_ROOT_DIR: /opt/hostedtoolcache/PyPy/3.9.12/x64
    Python3_ROOT_DIR: /opt/hostedtoolcache/PyPy/3.9.12/x64
    PKG_CONFIG_PATH: /opt/hostedtoolcache/PyPy/3.9.12/x64/bin/lib/pkgconfig
python create: /home/runner/work/cmdix/cmdix/.tox/python
python installdeps: pytest >= 6.2.1
python develop-inst: /home/runner/work/cmdix/cmdix
/home/runner/work/_temp/8f22a1bd-6a25-45f6-9a61-1150bb55390b.sh: line 1:  1706 Killed                  tox
Error: Process completed with exit code 137.