doctest.set_unittest_reportflags

        def set_unittest_reportflags(flags):
    """Sets the unittest option flags.

    The old flag is returned so that a runner could restore the old
    value if it wished to:

      >>> import doctest
      >>> old = doctest._unittest_reportflags
      >>> doctest.set_unittest_reportflags(REPORT_NDIFF |
      ...                          REPORT_ONLY_FIRST_FAILURE) == old
      True

      >>> doctest._unittest_reportflags == (REPORT_NDIFF |
      ...                                   REPORT_ONLY_FIRST_FAILURE)
      True

    Only reporting flags can be set:

      >>> doctest.set_unittest_reportflags(ELLIPSIS)
      Traceback (most recent call last):
      ...
      ValueError: ('Only reporting flags allowed', 8)

      >>> doctest.set_unittest_reportflags(old) == (REPORT_NDIFF |
      ...                                   REPORT_ONLY_FIRST_FAILURE)
      True
    """
    global _unittest_reportflags

    if (flags & REPORTING_FLAGS) != flags:
        raise ValueError("Only reporting flags allowed", flags)
    old = _unittest_reportflags
    _unittest_reportflags = flags
    return old