Avoid usage of packaging in non-test code

[jorisvandenbossche]

See #316 (comment), this avoids adding it as an actual dependency.

[martinfleis]

As long as this is the only case of version checking I guess it is fine to do it manually like this. But if we'll need it on more occasions in future, I would just add packaging as a dependency. Given the low number of deps we have here, let's try it without but I am not sure how long it will take :).

[brendan-ward]

Does this also warrant a changelog entry for 0.7.1?

[jorisvandenbossche]

Sorry, this is really stupid. I just went from the error I saw on the conda-forge build, and didn't do a proper search for the usage of packaging, and we are also still using it in _compat.py ... and so 0.7.1 didn't fix the issue.

I suppose we then just add packaging to the dependencies?

[martinfleis]

I suppose we then just add packaging to the dependencies?

That is probably the best option. We can revert this PR and add packaging as dependency here and then in meta on conda-forge.

[brendan-ward]

Sorry, this is my fault for adding it to verify shapely / pandas versions; easy to overlook because our dev / test environments already have it.

I'll try to get a fix in place a bit later today.