Consider an appropriate time to drop support for Python 3.5

[tleonhardt]

The recent Python Developers Survey 2019 Results show that only 4% of Python 3 users are still using Python 3.5

Python 3.5 is scheduled to be end-of-life in September 2020. Major projects like Django have already dropped support for Python 3.5 for new versions. We should plan for when we want cmd2 to stop supporting Python 3.5

By moving to support 3.6+ we open up the ability to use things like f-strings, syntax for variable annotations, and pathlib.

[kmvanbrunt]

I'm OK removing support but we should give sufficient advanced warning. I know Debian 9 has Python 3.5 as it's default, so cmd2 developers on that system will need to upgrade Python for new cmd2 features.

[tleonhardt]

I recommend that before we put out the 1.1 release, lets update the README to remove the old warning about dropping support for Python 2.7 and add a new warning about dropping support for Python 3.5, say perhaps August 31, 2020.

[kotfu]

Sounds good to me. What will the version number of cmd2 be for the first release we drop python 3.5 support? 2.0?

[tleonhardt]

Good question about version after we drop support for Python 3.5 .... Yeah I guess 2.0 might be the right answer in that case.

[kotfu]

I'm not certain that 2.0 is the right version number we should use. I was just thinking of how Requests didn't drop support for python 2.7 and 3.5 in their 2.x series. 3.x will only support python 3.6+. But they had lots of other changes in requests 3.x too. Django did the same thing, v3.0 dropped support for python 3.5 and older.

[tleonhardt]

I'm not certain of the right answer either. I think 1.2 or 1.3 or whatnot could be fine as well.

[anselor]

Things to do when we cut 3.5 support:

• travis.yml, noxfile.py - remove the special 3.5.x test handling. Remove conditional checks related to 3.5.x
• utils.py - restore type annotations for get_defining_class
• setup.py - Remove conditional module dependencies for 3.5.x
• table_creator.py - Remove fallback redeclaration of typing.Deque needed for versions earlier than 3.5.4.
• cmd2.py, many others - Every instance of self.var_name = [something] #type: type-declaration can be replaced with self.var_name: type-declaration = [something]

[tleonhardt]

I already removed Python 3.5 testing already in PR #1051 - it was failing in GitHub Actions for reasons related it to being significantly past its EOL.

So I think we should drop 3.5 support ASAP. I'm happy if we do that as in a 1.5 release or if we put out 2.0 soon. But we shouldn't delay since we will no longer have continuous integration testing for Python 3.5 (any version).

[tleonhardt]

Since the 2.0 branch has been merged into the main branch, we should be able to drop support for 3.5 any time now.