[Python-modules-team] Bug#893360: python3-tornado 5.0.0 breaks python3-zmq

[Michael Olbrich]

Package: python3-tornado
Version: 5.0.0-1
Severity: normal

Dear Maintainer,

I'm using python3-tornado indirectly with IPython. With the update to
python3-tornado 5.0.0-1 this is broken. The testcase to reproduce this is
simple:

import IPython
IPython.embed_kernel()

With the new version this results in:

Traceback (most recent call last):
  File "./test.py", line 3, in <module>
    IPython.embed_kernel()
  File "/usr/lib/python3/dist-packages/IPython/__init__.py", line 91, in embed_kernel
    real_embed_kernel(module=module, local_ns=local_ns, **kwargs)
  File "/usr/lib/python3/dist-packages/ipykernel/embed.py", line 38, in embed_kernel
    app.initialize([])
  File "<decorator-gen-121>", line 2, in initialize
  File "/usr/lib/python3/dist-packages/traitlets/config/application.py", line 87, in catch_config_error
    return method(app, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/ipykernel/kernelapp.py", line 452, in initialize
    zmq_ioloop.install()
  File "/usr/lib/python3/dist-packages/zmq/eventloop/ioloop.py", line 210, in install
    assert (not ioloop.IOLoop.initialized()) or \
AttributeError: type object 'IOLoop' has no attribute 'initialized'

It seems to me that the python3-tornado API changed in version 5.x and
python3-zmq does not support this. I'm using python3-zmq 16.0.2-2+b1 and
python3-ipykernel 4.8.2-2 here.

Downgrading python3-tornado to 4.5.3-1 'fixes' the problem for me.

-- System Information:
Debian Release: buster/sid
  APT prefers experimental
  APT policy: (900, 'experimental'), (900, 'unstable'), (600, 'testing'), (550, 'stable'), (500, 'unstable-debug'), (500, 'testing-debug')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.15.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8), LANGUAGE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages python3-tornado depends on:
ii  ca-certificates  20170717
ii  libc6            2.27-2
ii  python3          3.6.4-1

python3-tornado recommends no packages.

Versions of packages python3-tornado suggests:
pn  python-tornado-doc  <none>
ii  python3-pycurl      7.43.0.1-0.2
pn  python3-twisted     <none>

-- no debconf information