tom-buf

@contextmanager
def modified_environ(**overlay):
    """
    XXX FIXME

    >>> ...
    """
    def _update_environ(d):
        for k, v in d.items():
            yield k, os.environ.pop(k, None)

            if v is not None:
                os.environ[k] = v

    # Modify os.environ in place, saving original values for restore later
    original = dict(_update_environ(overlay))

    try:
        yield
    finally:
        # Restore os.environ to as it was
        _update_environ(original)