Fixed on PyPy

Author: YannickJadoul

include/pybind11/cast.h

@@ -1041,10 +1041,11 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
             handle obj = src;
 #if PY_VERSION_HEX < 0x03080000
             bool do_decref = false;
-            if (PyIndex_Check(src.ptr())) {
+            if (index_check(src.ptr())) {
                 PyObject *tmp = PyNumber_Index(src.ptr());
                 if (!tmp) {
-                    py_value = (py_type) -1;
+                    PyErr_Clear();
+                    return false;
                 }
                 do_decref = true;
                 obj = tmp;