Work around unittest issue with pytest 5.4.{0,1}

Ref: pytest-dev#824

pytest_django/plugin.py

@@ -507,20 +507,16 @@ def _django_setup_unittest(request, django_db_blocker):
         yield
         return
 
-    from _pytest.unittest import TestCaseFunction
+    # Fix/patch pytest.
+    # Before pytest 5.4: https://github.com/pytest-dev/pytest/issues/5991
+    # After pytest 5.4: https://github.com/pytest-dev/pytest-django/issues/824
+    from _pytest.monkeypatch import MonkeyPatch
 
-    if "debug" in TestCaseFunction.runtest.__code__.co_names:
-        # Fix pytest (https://github.com/pytest-dev/pytest/issues/5991), only
-        # if "self._testcase.debug()" is being used (forward compatible).
-        from _pytest.monkeypatch import MonkeyPatch
+    def non_debugging_runtest(self):
+        self._testcase(result=self)
 
-        def non_debugging_runtest(self):
-            self._testcase(result=self)
-
-        mp_debug = MonkeyPatch()
-        mp_debug.setattr("_pytest.unittest.TestCaseFunction.runtest", non_debugging_runtest)
-    else:
-        mp_debug = None
+    mp_debug = MonkeyPatch()
+    mp_debug.setattr("_pytest.unittest.TestCaseFunction.runtest", non_debugging_runtest)
 
     request.getfixturevalue("django_db_setup")
 

tests/test_unittest.py

@@ -58,10 +58,11 @@ def tearDown(self):
 
 def test_sole_test(django_testdir):
     """
-    Make sure the database are configured when only Django TestCase classes
+    Make sure the database is configured when only Django TestCase classes
     are collected, without the django_db marker.
-    """
 
+    Also ensures that the DB is available after a failure (#824).
+    """
     django_testdir.create_test_module(
         """
         import os
@@ -80,12 +81,27 @@ def test_foo(self):
 
                 # Make sure it is usable
                 assert Item.objects.count() == 0
+
+                assert 0, "trigger_error"
+
+        class TestBar(TestCase):
+            def test_bar(self):
+                assert Item.objects.count() == 0
     """
     )
 
     result = django_testdir.runpytest_subprocess("-v")
-    result.stdout.fnmatch_lines(["*TestFoo*test_foo PASSED*"])
-    assert result.ret == 0
+    result.stdout.fnmatch_lines(
+        [
+            "*::test_foo FAILED",
+            "*::test_bar PASSED",
+            '>       assert 0, "trigger_error"',
+            "E       AssertionError: trigger_error",
+            "E       assert 0",
+            "*= 1 failed, 1 passed in *",
+        ]
+    )
+    assert result.ret == 1
 
 
 class TestUnittestMethods: