JS services test failure on Python 2.7

[takluyver]

Tests on Python 2.7 on Travis are failing like this:

FAIL one kernel running
#    type: assertEquals
#    file: /home/travis/build/jupyter/notebook/notebook/tests/services/kernel.js
#    subject: 2
#    expected: 1

FAIL one session running
#    type: assertEquals
#    file: /home/travis/build/jupyter/notebook/notebook/tests/services/session.js
#    subject: 4
#    expected: 1

@blink1073 was starting to investigate on #3120, but we haven't worked it out yet.

[blink1073]

Is Python 2.7 dead yet? Oh what a happy day that would be....

[takluyver]

I was thinking of aiming for notebook 6.0 and requiring Py 3 next year. But I think we'll need to figure this out one way or the other.

[blink1073]

Agreed on both

[takluyver]

It looks like for some reason it's starting a python3 kernel as well as the python2 one. :-/

[takluyver]

I think I know where it's coming from. Investigating using #3128.

[takluyver]

It wasn't where I was thinking - it turns out it was actually a problem with ipykernel: ipython/ipykernel#288 . I've made a workaround in #3128.