Back in February I pinned the coverage module for Python 3.4 in our toolchain to <5.0, since coverage 5 dropped support for Python 3.4. I didn't pin the version of coverage for newer Python versions or Python 2.7. Since that version of the toolchain was deployed the coverage task has failed with the following error:

[2021/06/16 22:53:16.074] Coverage.py warning: Couldn't use data file '/data/mci/a5c40ecd54988e9fa5b1e154c57d0dbc/src/coverage/coverage.tests-python-version-amazon1-without-c-extensions__platform~awslinux_auth-ssl~noauth-nossl_python-version~3.4_c-extensions~without-c-extensions_coverage~coverage.test-3.4-standalone': Looks like a coverage 4.x data file. Are you mixing versions of coverage?

The simplest solution to this problem is just to stop running coverage with Python 3.4, since PyMongo 3.12 will be the last version to support 3.4.

*edit*

Coverage 5+ now requires sqlite, and sqlite headers are not currently available on all of our test infrastructure. To fix that we can pin to coverage<5, then get sqlite headers installed on the right machines and rebuild the toolchain with support.