Issue 14135: check for locale changes in test.regrtest

I had to back out this changeset as it totally broke the test suite here:

[ 91/372/90] test_defaultdict
test test_defaultdict crashed -- Traceback (most recent call last):
  File "/home/antoine/cpython/default/Lib/test/regrtest.py", line 1287, in runtest_inner
    with saved_test_environment(test, verbose, quiet) as environment:
  File "/home/antoine/cpython/default/Lib/test/regrtest.py", line 1251, in __enter__
    in self.resource_info())
  File "/home/antoine/cpython/default/Lib/test/regrtest.py", line 1250, in <genexpr>
    self.saved_values = dict((name, get()) for name, get, restore
  File "/home/antoine/cpython/default/Lib/test/regrtest.py", line 1237, in get_locale
    return tuple(map(locale.getlocale, self._locale_categories))
  File "/home/antoine/cpython/default/Lib/locale.py", line 523, in getlocale
    raise TypeError('category LC_ALL is not supported')
TypeError: category LC_ALL is not supported

(etc.)