Supports Python3

[smellman]

• continue #238 branch
• remove travis-ci and add supports github actions
• ~resource tag seems deprecated so I remove resource tag and use asset tag.~

~This PR doesn't support Python2 for CI and I test with only python3 environment.~

[Zharktas]

However, we can't remove python2 support from core extensions as long as python2 versions of ckan is still under support eg. ckan 2.8.

[smellman]

@Zharktas OK, I will try to support ckan 2.8, 2.9-python2, 2.9 and master.

[smellman]

• github actions supports ckan 2.7, 2.8, 2.9-py2 and 2.9 with docker test images and remove ci for ckan master branch
• fixes some logics for ci in ckan 2.7 and 2.8

[howff]

I have just tested the branch https://github.com/smellman/ckanext-spatial/tree/dev-py3 in ckan-2.9 python3 ubuntu20.04 and it worked for me (unlike the current ckan/ckanext-spatial which did not)

[bonnland]

Any idea when this could get merged? My organization is trying to move to CKAN 2.9 and python 3, and we rely heavily on this extension (harvesting ISO 19139).

Thanks for any info!

[tomeksabala]

I have also run some preliminary tests with this WIP branch on my CKAN 2.9 setup and it seemed to work. I am also really interested on what's the timeline for getting this merged in!

Thanks for a great work @smellman

[tino097]

+1 to be merged @ckan/core

[amercader]

I'll do a final review this week, thanks @smellman and @smotornyuk for your work on this!

[amercader]

I've merged this branch plus a bunch of improvements and fixes to make it more future-proof (you can check commits 17c7ffd37fdfef4e354c3596b5a2b47d6abe3808 to 90ee774c86ea148eeb04905f9e8761c365df3fa8) and tagged it v1.0.0

Huge thanks to @smellman for finishing the great work that @smotornyuk started and taking this over the line.