Investigate OTP test failure

[ktohalloran]

While running python3 -Wall manage.py test from /opt/app/python/cac_tripplanner, the test_isochrone_partiitioning test failed with the following error:

This error appeared to be related to the machine's OTP instance and occurred on a machine with the following specs:

• MacOS Monterey version 12.3.1
• VirtualBox version 6.1.32
• Vagrant version 2.2.18

This failure does not occur on every machine; we need to figure out why it occurs on some and how to fix it.