* use unittest.main() instead of run_unittest(test_suite()) to run tests from
modules via the CLI
* add explicit load_tests() to load doctests
* use test.support.load_package_tests() to load tests in submodules of
distutils.tests
* removes no longer needed test_suite() functions
Use "backslashreplace" instead of "unicode-escape". It is not
implementation depended and escapes only non-encodable characters.
Also simplify the code.