bpo-39884: Add method name in "bad call flags" error (GH-18944) (GH-18957)

_PyMethodDef_RawFastCallDict() and _PyMethodDef_RawFastCallKeywords()
now include the method name in the SystemError "bad call flags" error
message to ease debug.

(cherry picked from commit c7d2d69)

Author: vstinner

Misc/NEWS.d/next/C API/2020-03-12-00-27-26.bpo-39884.CGOJBO.rst

@@ -0,0 +1,3 @@
+:c:func:`_PyMethodDef_RawFastCallDict` and
+:c:func:`_PyMethodDef_RawFastCallKeywords` now include the method name in the
+SystemError "bad call flags" error message to ease debug.

Objects/call.c

@@ -554,9 +554,8 @@ _PyMethodDef_RawFastCallDict(PyMethodDef *method, PyObject *self,
     }
 
     default:
-        PyErr_SetString(PyExc_SystemError,
-                        "Bad call flags in _PyMethodDef_RawFastCallDict. "
-                        "METH_OLDARGS is no longer supported!");
+        PyErr_Format(PyExc_SystemError,
+                     "%s() method: bad call flags", method->ml_name);
         goto exit;
     }
 
@@ -702,9 +701,8 @@ _PyMethodDef_RawFastCallKeywords(PyMethodDef *method, PyObject *self,
     }
 
     default:
-        PyErr_SetString(PyExc_SystemError,
-                        "Bad call flags in _PyMethodDef_RawFastCallKeywords. "
-                        "METH_OLDARGS is no longer supported!");
+        PyErr_Format(PyExc_SystemError,
+                     "%s() method: bad call flags", method->ml_name);
         goto exit;
     }