PR: Make compatible with Spyder 6

[mrclary]

@jitseniesen, I don't know what the release strategy is for spyder-notebook.
I believe this will be a breaking change, so this will only be compatible with certain Spyder versions. Let me know what you'd like to do.

[jitseniesen]

Spyder-notebook 0.5.x is compatible with Spyder 5.x only. The master branch will become spyder-notebook 0.6.0 and be compatible with 6.x only. I am not sure this is the best approach, but it is what I eventually settled on for all the plugins that I maintain.

If I remember correctly, your first commit (updating the import of shorten_paths) is already in the master branch but the second one is not - but I did not check. Feel free to let me take care of it; alternatively, target the master branch with this PR.

[mrclary]

Spyder-notebook 0.5.x is compatible with Spyder 5.x only. The master branch will become spyder-notebook 0.6.0 and be compatible with 6.x only. I am not sure this is the best approach, but it is what I eventually settled on for all the plugins that I maintain.

If I remember correctly, your first commit (updating the import of shorten_paths) is already in the master branch but the second one is not - but I did not check. Feel free to let me take care of it; alternatively, target the master branch with this PR.

Thanks for clarifying. I'll fix it them to be on the correct branch. I'm not challenging your approach, I just want to understand that we can know how best to move forward.

[jitseniesen]

Closing because this PR is subsumed by PR #457