Return self.trace_dispatch from dispatch_return() to enable stepping through…

Return self.trace_dispatch from dispatch_return() to enable stepping through generators. (An alternative would be to create a new "yield" debugger event, but that involves many more changes, and might break Bdb subclasses.)

Lib/bdb.py

@@ -74,6 +74,7 @@ class Bdb:
         if self.stop_here(frame) or frame == self.returnframe:
             self.user_return(frame, arg)
             if self.quitting: raise BdbQuit
+        return self.trace_dispatch
 
     def dispatch_exception(self, frame, arg):
         if self.stop_here(frame):