Make PyTraceBack_Here use the current thread, not the
frame's thread state. Fixes #1579370.
Will backport.
diff --git a/Python/traceback.c b/Python/traceback.c
index cfbd833..4ddee2c 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -113,7 +113,7 @@
 int
 PyTraceBack_Here(PyFrameObject *frame)
 {
-	PyThreadState *tstate = frame->f_tstate;
+	PyThreadState *tstate = PyThreadState_GET();
 	PyTracebackObject *oldtb = (PyTracebackObject *) tstate->curexc_traceback;
 	PyTracebackObject *tb = newtracebackobject(oldtb, frame);
 	if (tb == NULL)