Fail testrun on test failure

Dan Bungertrequested to merge
dbungert/iniparser:testrun-exit-1 into master

Test failures can go unnoticed, as currently the test runner unconditionally returns exit code 0. Consult the number of test failures and exit code 1 if there are any.

Similar PR upstream at: https://github.com/ndevilla/iniparser/pull/130

Also tweak the rules clean while I'm here.

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