DEP: drop support for older versions of dependencies

[martinfleis]

Updated CI and requirements as per #1457, removed compatibility layers for older pandas and fiona.

This also removes support for Python 3.5.

[jorisvandenbossche]

Thanks for working on this! (and a nice clean-up, especially for fiona ;))

One thing I am wondering: should we add a check on import if the minimum version is met?
Eg when the user has pandas < 0.24, raise a more informative import error message about GeoPandas requiring pandas >= 0.24.

For something we know will definitely fail otherwise, this might be good to do (eg for pandas, this will fail with an import error about register_extension_dtype on import of geopandas).
For ones where many functionality might still work (eg fiona), I am less sure about it.

[martinfleis]

should we add a check on import if the minimum version is met?

I don't think so, normally you should not even end with such an environment, since both pip and conda resolve dependencies based on our requirements. And if you manage to do so, you should be able to figure out what is wrong I'd say.

[jorisvandenbossche]

Ah, yes, for required dependencies we can indeed enforce that through installation, I forgot about that.
But you can update setup.py then:

geopandas/setup.py

Line 32 in b0381e1

INSTALL_REQUIRES = ["pandas >= 0.23.0", "shapely", "fiona", "pyproj >= 2.2.0"]

I was mostly thinking about how we do this in pandas, but there we have a huge number of optional dependencies, for which a version cannot be enforced in install requirements.

[martinfleis]

But you can update setup.py

As I was changing all requirements and environments I forgot about this :). Done.

[jorisvandenbossche]

All good from my side. I would maybe just wait a moment with merging if we make a 0.8.1 release

[martinfleis]

if we make a 0.8.1 release

I would do one once pickle issue is resolved.

[martinfleis]

0.8.1 released, merging.

[jorisvandenbossche]

Thanks Martin!