I tried to land a CL:
https://chromium-review.googlesource.com/c/catapult/+/870873

Which, however, incorporated a typo (the CleanUpEnvironment method belongs to possible_browser, not browser_options).

The error should have been caught when running e.g.

$ ./telemetry/bin/run_browser_tests SimpleBrowserTest --browser=stable

however it looks like exceptions during tear down are silently ignored. So the mistake slipped through catapult's CQ, and was only caught later by external clients which call the offending method *outside* the context of a tear down.

The root of the issue appears to come from:
https://github.com/dpranke/typ/blob/1e254b3ef4d14dee6109d8c3a58ab64d1500e3c2/typ/runner.py#L816

where typ silently ignores exceptions during teardown.

+dpranke this doesn't seem to be an ideal situation, what would you suggest as a way of moving forward?

From python's unittest documentation it sounds like a similar situation there *would* report an error, c.f.:
https://docs.python.org/2/library/unittest.html#class-and-module-fixtures