def unicode_is_ascii(u_string):
    """Determine if unicode string only contains ASCII characters.

    :param str u_string: unicode string to check. Must be unicode
        and not Python 2 `str`.
    :rtype: bool
    """
    assert isinstance(u_string, str)
    try:
        u_string.encode('ascii')
        return True
    except UnicodeEncodeError:
        return False
Determine if unicode string only contains ASCII characters.

    :param str u_string: unicode string to check. Must be unicode
        and not Python 2 `str`.
    :rtype: bool
    
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_vendor/requests/_internal_utils.py