AttributeError: module 'pyximport.pyximport' has no attribute 'get_distutils_extension'

[qci-amos]

Bug Description

My CI builds are suddenly erroring out:

../../../virtualenv/python3.8.13/lib/python3.8/site-packages/my_code.py:14: in <module>
    import qutip
../../../virtualenv/python3.8.13/lib/python3.8/site-packages/qutip/__init__.py:64: in <module>
    import qutip.cy.pyxbuilder as _pyxbuilder
../../../virtualenv/python3.8.13/lib/python3.8/site-packages/qutip/cy/pyxbuilder.py:17: in <module>
    old_get_distutils_extension = pyximport.pyximport.get_distutils_extension
E   AttributeError: module 'pyximport.pyximport' has no attribute 'get_distutils_extension'

Code to Reproduce the Bug

import qutip

Code Output

No response

Expected Behaviour

no exception

Your Environment

I'm using `qutip-4.7.2-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl`.

Additional Context

This exact same environment was working in yesterday's CI build. We speculate that Cython's major release yesterday is related.

[Ericgig]

Thank you for reporting.
Yes, Qutip does not work with cython 3.0.0.
I found a bug in cython trying to fix it so the patch could take some time.

[qci-amos]

Ah, I see now that you do have a pin:

qutip/requirements.txt

Line 1 in efd39be

cython>=0.29.20,<3.0.0

but there hasn't been a release since that change.

[qci-amos]

I think this has been resolved by #2220