dockerpty.start doesn't return after detaching container

[plehong]

I'm trying to run an interactive shell in a docker container, but dockerpty.start doesn't return when I detach the container using C-p C-q.

On RedHat 7.2, it remains stuck in the _hijack_tty method.
On Ubuntu 14.4, I get an exception if I continue to enter some keystrokes.

Attached file contains the test program and the traceback on Ubuntu, Docker version 1.10.1.

Test.zip

[plehong]

As stated in the README.md: "If you press C-p C-q, the container's PTY will be closed, but the container will keep running. In other words, you will have detached from the container and can re-attach with another dockerpty.start() call."
So i consider this issue as a BUG and not an ENHANCEMENT, since the PTY isn't properly closed.