Can't test Stability because it overrides Pkg.test

[ulysses4ever]

As a result of interjecting (a part of) functionality of Pkg.test (in src/pkg-test-override.jl), I can't
run tests for the Stability package itself, which is sad. I thought I could give away
with a sort of conditional inclusion of the relevant code, but for an unknown reason
the mere presence of the code in the package seems to interfere with Pkg.test.