problem with python3 str

[tdaff]

Original report by Jean-Marc Andreoli (Bitbucket: jmandreoli, GitHub: jmandreoli).

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The following lines (600-602) in kernel.py, which decode self.host, cause an error with slurm (and probably some other launchers), as the decoding happens too late.

#!python

# zmq needs str in Python 3, but pexpect gives bytes
if hasattr(self.host, 'decode'):
  self.host = self.host.decode('utf-8')

And furthermore, there is no need to do the decoding again and again each time tunnel_cmd is invoked.

My fix: Move them just after launch_* but before start_kernel at line 240

[tdaff]

Original comment by Matthias Bussonnier (Bitbucket: Carreau, GitHub: Carreau).

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It's actually assign in a ton of places. I have a patch making it working on slurm, and force the assigment to always be string using Traitlets. I'm hitting other issues on slurm (mostly expect('exit') to block), but I should be able to send a patch soon.

[tdaff]

Original comment by Jean-Marc Andreoli (Bitbucket: jmandreoli, GitHub: jmandreoli).

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Just FYI, I implemented the simple fix I mention in my comment (move the lines of code) and had no problem with slurm since then. remote_ikernel is a cool package, it would be nice if it could natively be integrated in jupyter, where the method to select a kernel could be split into the choice of kernel itself and the choice of launcher, instead of the current single scroll down menu combining both. Do you know if there are any plans along that line ? I am not familiar with the jupyter development process, but I for one would definitely support that feature.

[tdaff]

Original comment by Matthias Bussonnier (Bitbucket: Carreau, GitHub: Carreau).

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You could definitely have a kernel manager that does it, but one of the problem is interoperability.
You need many pieces that are "Jupyter aware" to reimplement it instead if you "bake" that into jupyter.
One of the advantages here is that it will work with classic jupyter, nteract, papermill, hydrogen, .... etc So there is a strong incentive to keep pieces separated.

I've send https://bitbucket.org/tdaff/remote_ikernel/pull-requests/5/ensure-selfhost-is-always-unicode/diff that should fix that more globally across launchers.