Add related and details.rst to 'redundant-unittest-assert' style message's doc

doc/data/messages/r/redundant-unittest-assert/bad.py

@@ -4,3 +4,8 @@
 class DummyTestCase(unittest.TestCase):
     def test_dummy(self):
         self.assertTrue("foo")  # [redundant-unittest-assert]
+
+
+def test_division():
+    a = 9 / 3
+    assert "No ZeroDivisionError were raised"  # assert-on-string-literal

doc/data/messages/r/redundant-unittest-assert/details.rst

@@ -1 +1,2 @@
-Directly asserting a string literal will always pass.
+Directly asserting a string literal will always pass. The solution is to
+test something that could fail, or not assert at all.

doc/data/messages/r/redundant-unittest-assert/good.py

@@ -3,5 +3,9 @@
 
 class DummyTestCase(unittest.TestCase):
     def test_dummy(self):
-        actual = "test_result"
-        self.assertEqual(actual, "expected")
+        # Nothing, as an assert of a string literal will always pass
+        pass
+
+def test_division():
+    a = 9 / 3
+    assert a == 3

doc/data/messages/r/redundant-unittest-assert/related.rst

@@ -0,0 +1,3 @@
+- `Tests without assertion <https://stackoverflow.com/a/137418/2519059>`_
+- `Testing that there is no error raised <https://stackoverflow.com/questions/20274987>`_
+- `Parametrizing conditional raising <https://docs.pytest.org/en/latest/example/parametrize.html#parametrizing-conditional-raising>`_