GH-100530: Change the error message for non-class class patterns (GH-103576)

Author: sobolevn

Misc/NEWS.d/next/Core and Builtins/2023-04-16-14-38-39.gh-issue-100530.OR6-sn.rst

@@ -0,0 +1 @@
+Clarify the error message raised when the called part of a class pattern isn't actually a class.

Python/ceval.c

@@ -416,7 +416,7 @@ match_class(PyThreadState *tstate, PyObject *subject, PyObject *type,
             Py_ssize_t nargs, PyObject *kwargs)
 {
     if (!PyType_Check(type)) {
-        const char *e = "called match pattern must be a type";
+        const char *e = "called match pattern must be a class";
         _PyErr_Format(tstate, PyExc_TypeError, e);
         return NULL;
     }