Replace case.patching fixture with mockeypatch + MagicMock

requirements/test.txt

@@ -1,4 +1,3 @@
-case>=1.3.1
 pytest-django>=4.5.2,<5.0
 pytest>=6.2.5,<8.0
 pytest-timeout

t/unit/conftest.py

@@ -1,3 +1,5 @@
+from unittest.mock import MagicMock
+
 import pytest
 # we have to import the pytest plugin fixtures here,
 # in case user did not do the `python setup.py develop` yet,
@@ -40,3 +42,11 @@ def add(x, y):
     yield
     if request.instance:
         request.instance.app = None
+
+
+@pytest.fixture
+def patching(monkeypatch):
+    def _patching(attr):
+        monkeypatch.setattr(attr, MagicMock())
+
+    return _patching