Sync mypy and bump to 0.4.0

Author: ilevkivskyi

lib-rt/exc_ops.c

@@ -1,3 +1,5 @@
+#include "pythoncapi_compat.h"
+
 // Exception related primitive operations
 //
 // These are registered in mypyc.primitives.exc_ops.
@@ -24,7 +26,7 @@ void CPy_Reraise(void) {
 }
 
 void CPyErr_SetObjectAndTraceback(PyObject *type, PyObject *value, PyObject *traceback) {
-    if (!PyType_Check(type) && value == Py_None) {
+    if (!PyType_Check(type) && Py_IsNone(value)) {
         // The first argument must be an exception instance
         value = type;
         type = (PyObject *)Py_TYPE(value);