tests/silenttestrunner.py

help: assigning categories to existing commands

I'm separating this into its own commit so people can bikeshed over the actual
categorization (vs the support for categories). These categories are based on
the help implementation we've been using internally at Google, and have had
zero complaints.

Differential Revision: https://phab.mercurial-scm.org/D5067

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