Convert to Python 3

[albireox]

• Make Python 3-only.
• Remove dependency on RO and move wrappers inside STUI / move them to their own package?
• Use newer version of py2app or test other packaging tools.
• Set reasonable minimum MacOS version.
• Test packaging for Linux.

[StarkillerX42]

Hey Jose,

I've upgraded a few things to Python 3, and I thought I might offer to help. Anaconda has a function that ships with it that handles the upgrade very well. The command
2to3-3.7 -nW RO
will handle 99% of the conversion.

As for building on Linux, I made a pull request that uses pyinstaller, which works well on Ubuntu, although I can't get it to connect, but I don't think that has anything to do with the build.

-Dylan

[r-owen]

I think futurize does an even better job.

[albireox]

@StarkillerX42 It would be great if you can push your initial Python 3 conversion to a new branch. Did you convert only RO or both RO and STUI (and, I guess, opscore)? Also, I keep meaning to comment on your PR but keep forgetting about it. Will do that now.

I have migrated opscore to Python 3 and tested it; it should work fine. I have also migrated actorcore and actorkeys.

@r-owen I guess the question is whether we want to keep both 2 and 3 compatibility or just 3. Since STUI is self-contained I was thinking to migrate to only 3. For that I have been using 2to3. My understanding is that futurize only does 2/3 compatibility. Are there other reasons why futurize is a better choice?

[r-owen]

I was thinking of a different package. 2to3 is probably an excellent choice.

I strongly agree that going to Python 3 with no backwards compatibility is the best thing to do. Code that is compatible with both is an awkward hybrid that is difficult to test and maintain and I see no need to maintain that backward compatibility.