Fix: Always use root node as location if there is no call node.

Author: fangerer

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/frame/ReadCallerFrameNode.java

@@ -167,15 +167,15 @@ public Frame visitFrame(FrameInstance frameInstance) {
                                 // avoid overriding the location if we don't know it
                                 if (callNode != null) {
                                     info.setCallNode(callNode);
-                                } else if (pRootNode.isPythonInternal()) {
+                                } else {
                                     // In some special cases we call without a Truffle call node; in
                                     // this case, we use the root node as location (e.g. see
                                     // AsyncHandler.processAsyncActions).
                                     info.setCallNode(pRootNode);
                                 }
                                 // We may never return a frame without location because then we
                                 // cannot materialize it.
-                                assert info.getCallNode() != null : "tried to read frame without location";
+                                assert info.getCallNode() != null : "tried to read frame without location (root: " + pRootNode + ")";
                                 return frame;
                             }
                             i += 1;