Rasterio: End of Support for Python 2.x

[snowman2]

Python 2.7 is reaching End Of Life and will no longer be supported by PSF from 1st January, 2020 (11 months from now).

https://www.python.org/dev/peps/pep-0373/
python/devguide#344

Should rasterio 1.0.x be the last version to support Python 2.x?

Related to https://github.com/Toblerity/Fiona/issues/716

[sgillies]

Discussion started: https://rasterio.groups.io/g/dev/message/85.

[sgillies]

Consensus: drop support for Python 2 in the master branch (to be 1.1).

[sgillies]

I've had a change of mind. For 1.1, which I'm interested in acceleration, let's note that we're going to drop support for Python 2 in the next release. I'll add a warning to the setup script and the rasterio.compat module for 1.1.