PyTket dependency is resolving badly

[mpharrigan]

The build is failing.

https://github.com/quantumlib/ReCirq/runs/1475828878?check_suite_focus=true#step:6:47

Need to check if they released a new version and why it's not backwards compatible. Pin or fix as necessary

[mpharrigan]

I can't reproduce this issue locally with the latest versions of pytket and pytket-cirq

[mpharrigan]

There might be something funky with the (new?) pip dependency resolver where it is installing pytket 0.6.1 (latest) but pytket-cirq 0.3 (old)

https://pypi.org/project/pytket-cirq/#history

[mpharrigan]

pytket-cirq 0.5 has the following install_requires

    install_requires=["pytket ~= 0.6", "cirq ~= 0.8.0"],

pytket-cirq 0.3 has this:

    install_requires=["pytket ~=0.5", "cirq ~=0.6"],

pytket-cirq 0.3.1 has this:

    install_requires=["pytket ~=0.5", "cirq == 0.8"],

So 0.3 is getting picked up because it has the loosest pin; but it breaks on import because the pytket dependency is too loose.

[mpharrigan]

If I pin all three packages, it warns that pip will break when they flip on the "new resolver".

[mpharrigan]

The pypa people -- with a straight face -- propose forking dependencies to work around these types of issues! https://pip.pypa.io/en/latest/user_guide/#loosen-the-requirements-of-your-dependencies