Revert use of ColoredTestRunner (#89)

[rly]

Motivation

Fix #578

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[rly]

This returns the test suite functionality for CI, i.e., python test.py -v to the old, kinda ugly formatting. But all the errors and tracebacks are printed at the bottom of the output, which makes debugging a lot easier, especially now that we have around 1000 tests. The coloredtestrunner format was just not usable.

Eventually we can move our testing framework to pytest and stop using our custom unittest-based solution.