End support for Python 2.7

[satterly]

Python 2.7 is EOL in 2020 and many python projects have decided to stop supporting Python 2.7 already.

The benefits of a Python 3 only codebase means that Alerta projects can take advantage of new features such as type hints.

It is proposed to make Alerta Release 5.2 and all dependent projects the last release to support Python 2.7. The proposal is that Python 2.7 support should be dropped 6 months from now. ie. 31 August 2018.

From this date, all future Alerta releases (ie. 6.x etc) will only support Python 3 with the last Python 2 release (5.2.x) only getting critical bug fixes.

[mmulqueen]

Fully agree with this proposal. We've been running Alerta with Python 3 since we've started using it, no issues. I've proposed some related changes to the documentation.

[satterly]

Worryingly, I've just learned that Click is recommending Python 2 for production environments due to unresolved Python 3 limitations. See http://click.pocoo.org/5/python3/ Click is used by the alerta CLI.

[d-ganchar]

Not sure that Python 2.7 support makes sense.
Better to use typing

[satterly]

@d-ganchar Exactly. That's why python 2.7 support will be withdrawn in less than 4 months from now.

[satterly]

IMPORTANT Support for Alerta on Python 2.7 will end in one month!!!

[satterly]

❗️ Note: An example of what needs to change in the deployment for an Apache/WSGI virtualenv environment on Debian/Ubuntu can be found here alerta/vagrant-try-alerta#13

[satterly]

Alerta server version 5.2.9 has just been published to Pypy and it is proposed that this is the last release to support Python 2.7. Only critical application bug fixes and security fixes will be applied to this branch in future.

Alerta server 6.0 will only support Python 3.5+ and will require Postgres 9.5+ or MongoDB 3.x.

[satterly]

Alerta client version 5.2.1 has just been published to Pypy and it will be the last release to support Python 2.7. Only critical application bug fixes and security fixes will be applied to this branch in future.

[satterly]

Limited support for Alerta on Python 2.7 will continue until support for Python 2.7 is officially dropped.

https://pythonclock.org/