tests/silenttestrunner.py

diffutil: extract diff options code into a dedicated util-module

We want to be able to create and use diffoptions in more places. Currently the
official function to instantiate diffoptions live into `mercurial.patch`. A
module too high level to be easily imported in some places.

So we extract the diff options related function in their own utility module.

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