wormhole send does not flush output when not connected to tty

[joeyh]

When I run run wormhole send somefile | less, I see these lines of stderr:

Warning: errors may occur unless both sides are running the same version
Server claims 0.8.2 is current, but ours is 0.8.1

And never any more output, until I press ctrl-c. Then the missing stdout finally gets displayed:

Sending 3 byte file named 'somefile'
On the other computer, please run: wormhole receive
Wormhole code is: 62-pandora-slowdown

Same thing happens when redirecting to a file, or when trying to intercept wormhole send's output for scripting.

It is apparently not flushing stdout when not connected to a tty.

This has stymied my attempts to extract the wormhole code from wormhole send.
(I suppose I could try to provide it with a pseudo-tty, and read what it outputs to the tty then but ...)