WIP: Preliminary investigation: updating to python 3

[drewsilcock]

So far:

• Moved dependencies over to Poetry (just made the process much easier with proper dependency resolution, doesn't need to be permanent change).
• Run 2to3 and hand-pick output to check for false positives. (Haven't run through every line of code to check for false negatives).
• Initial changes to fix immediate issues (blocked by not being able to import reporters_db currently, there's bound to be more issues after that though).
• Upgrade dependencies as required to get them installed on py3.8.

When porting code I tend to take this approach:

1. Upgrade dependencies until they install
2. Try to run code
3. It breaks
4. Fix where it breaks
5. Try to run code again
6. It breaks in a different place
7. Fix where it breaks again
8. Run it again: it breaks => goto 6. else continue
9. It works
10. Celebrate
11. Ah but this bit doesn't work... => goto 6
12. You get the idea

Next steps:

• Use mypy for an additional level of checking to find more issues without needing to run every line of code.
• Getting reporters_db installed and working on py3 so that we can continue with the porting cycle.

If you want to discuss any of these changes and potential problems, here's a good place to do it! 🙂

[drewsilcock]

I've pushed an update to replace mock with unittest.mock and remove the cl/cleanup directory, although it might make more sense to put those up as a PR against the python38-merger branch?

[drewsilcock]

p.s. Python 3.9 is now the latest stable version of Python, as of Monday. (Not that it's particularly important, just thought I'd mention.)

[mlissner]

We're incorporating these changes into our weirdly-named 1407-py3-unmerge branch and it has a bunch more changes, so I'm closing this one. Thanks for kicking this off, Drew. Huge deal.