fix mypy type narrowing in test_cli_security

tests/test_cli_security.py

@@ -18,7 +18,10 @@ def load_fpaste_module():
     )
     if spec is None or spec.loader is None:
         pytest.skip("Could not load fpaste module")
+        return None  # unreachable, but helps mypy
 
+    assert spec is not None  # mypy: narrow type after skip
+    assert spec.loader is not None
     fpaste = importlib.util.module_from_spec(spec)
     sys.modules["fpaste"] = fpaste
     spec.loader.exec_module(fpaste)