SF bug #963956: Bad error mesage when subclassing a module
Add a more informative message for the common user mistake of subclassing
from a module name rather than another class (i.e. random instead of
random.random).
diff --git a/Python/ceval.c b/Python/ceval.c
index 2cebf44..2d60014 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -3922,6 +3922,15 @@
}
result = PyObject_CallFunction(metaclass, "OOO", name, bases, methods);
Py_DECREF(metaclass);
+ if (result == NULL && PyErr_ExceptionMatches(PyExc_TypeError)) {
+ /* A type error here likely means that the user passed
+ in a base that was not a class (such the random module
+ instead of the random.random type). Help them out with
+ a more informative error message */
+ PyErr_SetString(PyExc_TypeError,
+ "Error when calling the metaclass.\n" \
+ "Make sure the base arguments are valid.");
+ }
return result;
}