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test/utils.py

@@ -118,7 +118,16 @@ def assertRaisesWithArg(self, exc_class, arg, func, *args, **kwargs):
         with pytest.raises(exc_class) as excinfo:
             func(*args, **kwargs)
         assert excinfo.value.args == (arg,)
-        # Explicitly clear the Exception Info 
+
+        # Explicitly clear the Exception Info. Citing https://docs.pytest.org/en/latest/reference.html#pytest-raises:
+        #
+        # Clearing those references breaks a reference cycle 
+        # (ExceptionInfo –> caught exception –> frame stack raising the exception 
+        # –> current frame stack –> local variables –> ExceptionInfo) which makes 
+        # Python keep all objects referenced from that cycle (including all local 
+        # variables in the current frame) alive until the next cyclic garbage collection 
+        # run. See the official Python try statement documentation for more detailed 
+        # information.
         del excinfo