Avoided unneeded assertion on Python 3

from django.test import TestCase

from django.test.utils import override_settings

from django.utils.encoding import force_str

from django.utils.six import binary_type, StringIO

from django.utils.six import binary_type, PY3, StringIO

def mock_inputs(inputs):

            class mock_getpass:

                @staticmethod

                def getpass(prompt=b'Password: ', stream=None):

                    if not PY3:

                        # getpass on Windows only supports prompt as bytestring (#19807)

                        assert isinstance(prompt, binary_type)

                    return inputs['password']