[Python-modules-team] Bug#942120: python3-zmq: pypy3 -m ipykernel install ... fails with No module named zmq.backend.cffi

[r.ductor]

Package: python3-zmq
Version: 17.1.2-3
Severity: normal

Dear Maintainer,

Maybe I'm missing some important point and maybe this does not concern python3-zmq, I report my issue anyway.

Just after successfull "aptitude install pypy3"
I tried to (system-wise) install ipython kernel for pypy3 and got the error below reported.

# pypy3 -m ipykernel install -name pypy3 -display-name PyPy3 && echo OK
Traceback (most recent call last):
  File "/usr/lib/pypy3/lib-python/3/runpy.py", line 183, in _run_module_as_main
    mod_name, mod_spec, code = _get_module_details(mod_name, _Error)
  File "/usr/lib/pypy3/lib-python/3/runpy.py", line 142, in _get_module_details
    return _get_module_details(pkg_main_name, error)                                                                         
  File "/usr/lib/pypy3/lib-python/3/runpy.py", line 109, in _get_module_details                                              
    __import__(pkg_name)                                      
  File "/usr/lib/python3/dist-packages/ipykernel/__init__.py", line 2, in <module>
    from .connect import *                                    
  File "/usr/lib/python3/dist-packages/ipykernel/connect.py", line 18, in <module>                                           
    import jupyter_client                                                                                                    
  File "/usr/lib/python3/dist-packages/jupyter_client/__init__.py", line 4, in <module>                                      
    from .connect import *
  File "/usr/lib/python3/dist-packages/jupyter_client/connect.py", line 23, in <module>
    import zmq
  File "/usr/lib/python3/dist-packages/zmq/__init__.py", line 47, in <module>
    from zmq import backend
  File "/usr/lib/python3/dist-packages/zmq/backend/__init__.py", line 40, in <module>
    reraise(*exc_info)
  File "/usr/lib/python3/dist-packages/zmq/utils/sixcerpt.py", line 34, in reraise
    raise value
  File "/usr/lib/python3/dist-packages/zmq/backend/__init__.py", line 27, in <module>
    _ns = select_backend(first) 
  File "/usr/lib/python3/dist-packages/zmq/backend/select.py", line 27, in select_backend
    mod = __import__(name, fromlist=public_api)
ModuleNotFoundError: No module named 'zmq.backend.cffi'

More info:

* I never used pip in this machine and never installed conda.

* I have python3-cffi-backend installed: 
# aptitude search python3-cffi-backend python3-zmq
i A python3-cffi-backend                                   - Foreign Function Interface for Python 3 calling C code - runtime
v   python3-cffi-backend-api-9729                          -                                                                 
v   python3-cffi-backend-api-max                           -                                                                 
v   python3-cffi-backend-api-min                           -                                                                 
p   python3-cffi-backend-dbg                               - Foreign Function Interface for Python 3 calling C code (Debug ve
i A python3-zmq                                            - Python3 bindings for 0MQ library                                
p   python3-zmq-dbg 

Thanks for your time

-- System Information:
Debian Release: bullseye/sid
  APT prefers testing
  APT policy: (900, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 5.2.0-2-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages python3-zmq depends on:
ii  libc6    2.28-10
ii  libzmq5  4.3.2-1
ii  python3  3.7.3-1

python3-zmq recommends no packages.

python3-zmq suggests no packages.

-- no debconf information