tests/silenttestrunner.py

tests: make test-worker.t pass on py2

I broke the py2 version in https://phab.mercurial-scm.org/D9287
because the `WorkerError.__bytes__()` (or `.__str__()`?) output was
different in py2 compared to py3. Part of the problem was that I
didn't propagate the status code that was passed in to the superclass
so it could get printed. This patch fixes that. I don't know how it
worked on py3 before this patch...

I also added the usual `__bytes__ = _tobytes` override for good
measure. It doesn't seem to be needed for tests to pass, though.

Differential Revision: https://phab.mercurial-scm.org/D9377

from __future__ import absolute_import, print_function
import os
import sys
import unittest


def main(modulename):
    '''run the tests found in module, printing nothing when all tests pass'''
    module = sys.modules[modulename]
    suite = unittest.defaultTestLoader.loadTestsFromModule(module)
    results = unittest.TestResult()
    suite.run(results)
    if results.errors or results.failures:
        for tc, exc in results.errors:
            print('ERROR:', tc)
            print()
            sys.stdout.write(exc)
        for tc, exc in results.failures:
            print('FAIL:', tc)
            print()
            sys.stdout.write(exc)
        sys.exit(1)


if os.environ.get('SILENT_BE_NOISY'):
    main = unittest.main