The "socket.unix" module exported only a function before
aa1b8cc9bc
when datagram support was added.
Fixes#1717
Thanks rsc and lucas for reporting and testing
This may in theory cause multiple disconnect events for the
adminstream client, if the only code using that wasn't calling
os.exit right away.
Hence, this should be a good enough partial fix for #1671. It is
not a full fix, because the shell will only notice the disconnect
after one has hit enter in the input; until then, it is stuck in
a read() call to stdin and completely oblivious to the disconnect.
