blocks.message_sink(gr.sizeof_float, msgq, 1)
that's the line getting the error. I think they've tightened up things a bit -
this rings a vague bell. You might try changing the third arg from 1 to True - this
might not be the only such place that needs changing. It's also possible that fixing
this error will just get slightly further with another error - let's hope not but if
so the next error might or might not be as easy to fix...
Max