Update SIGINT handler to not use the old interactive shell API

[adrianliaw]

Currently, when using Ctrl-C on the console that connects to an existing kernel, it raises an error:

Traceback (most recent call last):
  File "/Users/adrianliaw/.pyenv/versions/py351/bin/jupyter-console", line 9, in <module>
    load_entry_point('jupyter-console', 'console_scripts', 'jupyter-console')()
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_core/jupyter_core/application.py", line 267, in launch_instance
    return super(JupyterApp, cls).launch_instance(argv=argv, **kwargs)
  File "/Users/adrianliaw/.pyenv/versions/py351/lib/python3.5/site-packages/traitlets/config/application.py", line 596, in launch_instance
    app.start()
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_console/jupyter_console/app.py", line 150, in start
    self.shell.mainloop()
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_console/jupyter_console/ptshell.py", line 462, in mainloop
    self.interact()
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_console/jupyter_console/ptshell.py", line 454, in interact
    self.run_cell(code, store_history=True)
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_console/jupyter_console/ptshell.py", line 505, in run_cell
    self.handle_input_request(msg_id, timeout=0.05)
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_console/jupyter_console/ptshell.py", line 757, in handle_input_request
    req = self.client.stdin_channel.get_msg(timeout=timeout)
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_client/jupyter_client/blocking/channels.py", line 50, in get_msg
    ready = self.socket.poll(timeout)
  File "/Users/adrianliaw/.pyenv/versions/py351/lib/python3.5/site-packages/zmq/sugar/socket.py", line 503, in poll
    evts = dict(p.poll(timeout))
  File "/Users/adrianliaw/.pyenv/versions/py351/lib/python3.5/site-packages/zmq/sugar/poll.py", line 99, in poll
    return zmq_poll(self.sockets, timeout=timeout)
  File "zmq/backend/cython/_poll.pyx", line 122, in zmq.backend.cython._poll.zmq_poll (zmq/backend/cython/_poll.c:1850)
  File "zmq/backend/cython/_poll.pyx", line 115, in zmq.backend.cython._poll.zmq_poll (zmq/backend/cython/_poll.c:1705)
  File "zmq/backend/cython/checkrc.pxd", line 12, in zmq.backend.cython.checkrc._check_rc (zmq/backend/cython/_poll.c:2084)
  File "/Users/adrianliaw/Documents/projects/fork/jupyter_console/jupyter_console/app.py", line 122, in handle_sigint
    self.shell.write_err('\n')
AttributeError: 'ZMQTerminalInteractiveShell' object has no attribute 'write_err'

Clearly that app.py used an outdated API on ZMQTerminalInteractiveShell, this pull request fixed this.

[takluyver]

This will now print two newlines, whereas it was only one before. Can one of them be removed?

[takluyver]

Thanks, good catch. ZMQTerminalInteractiveShell used to inherit from IPython's InteractiveShell class, where that method was defined.

[adrianliaw]

@takluyver I just made a commit that removes the redundant line in the print statement, thanks!

[takluyver]

BTW, in general we ask people to configure their editor not to strip whitespace, because it inflates diffs and can lead to spurious merge conflicts. It doesn't matter much when it's only a few lines like here, but it's good to bear in mind if you contribute bigger changes. :-)

[takluyver]

Thanks! 🍪