Enforce ruff/bugbear rule B011

B011 Do not `assert False` (`python -O` removes these calls),
     raise `AssertionError()`

fsspec/tests/test_utils.py

@@ -381,7 +381,7 @@ def client(self):
             return mock
 
         def func_2(self):
-            assert False, "have to overwrite this"
+            raise AssertionError("have to overwrite this")
 
         def func_3(self):
             return "should succeed"