Import patch from stdlib unittest.mock instead of external mock (#277)

* Import patch from stdlib unittest.mock instead of external mock

* Resort the imports

Author: takis

setup.cfg

@@ -42,7 +42,6 @@ setup_requires =
     setuptools_scm
     pytest-runner
 tests_require =
-    mock
     pytest
     pytest-cov
     pytest-django

tests/test_types.py

@@ -1,8 +1,8 @@
 import logging
+from unittest.mock import patch
 
 import pytest
 from django.core.exceptions import ValidationError
-from mock import patch
 
 from tests import VALID_VIES_COUNTRY_CODE, VALID_VIES_IE, VALID_VIES_NUMBER
 from vies.types import VATIN