[ci] Deprecate flake8

[john-bodley]

CATEGORY

Choose one

• Bug Fix
• Enhancement (new features, refinement)
• Refactor
• Add tests
• Build / Development Environment
• Documentation

SUMMARY

This PR deprecates flake8 (where we were using flake8-import-order and flake8-mypy) in favor of using isort and mypy directly. Note pylint (which we use though in many cases have warnings disabled) can be viewed as a superset flake8.

The reasons for the changes are:

1. We've noticed in other repos that flake8-mypy has missed some issues that mypy discovers (fixed in this PR) and ignores some of the mypy settings.
2. We were using flake8 mostly for checking import order and typing now that we're using black. Note that isort both checks and formats.

Also we were using flake8 for some other checks but simply ignoring these via # noqa which lacked specificity, i.e., reading the code it's not apparent what we're ignoring. Ideally we should be upping our pylint game as these checks would be caught by pylint. Currently many files have pylint warnings ignored and we have disabled a number of checks in the .pylintrc file per here. In the future we enforce pylint for all errors and warning and enable most (if not all) checks.

There are a few cases where I used # type: ignore as I ended up going down a rabbit hole when trying to resolve types. I think in the future we should try to re-enable these checks.

TEST PLAN

CI.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

REVIEWERS

to: @betodealmeida @etr2460 @michellethomas @mistercrunch @villebro

[codecov-io]

Codecov Report

Merging #8409 into master will decrease coverage by 0.04%.
The diff coverage is 90.76%.

@@            Coverage Diff             @@
##           master    #8409      +/-   ##
==========================================
- Coverage   67.65%   67.61%   -0.05%     
==========================================
  Files         448      448              
  Lines       22506    22482      -24     
  Branches     2364     2364              
==========================================
- Hits        15227    15201      -26     
- Misses       7141     7143       +2     
  Partials      138      138

Impacted Files	Coverage Δ
superset/models/sql_types/presto_sql_types.py	72.41% <ø> (ø)	⬆️
superset/views/datasource.py	95.12% <ø> (ø)	⬆️
superset/examples/tabbed_dashboard.py	22.22% <ø> (ø)	⬆️
superset/examples/multiformat_time_series.py	15.38% <ø> (ø)	⬆️
superset/examples/birth_names.py	100% <ø> (ø)	⬆️
superset/examples/bart_lines.py	29.62% <ø> (ø)	⬆️
superset/examples/world_bank.py	100% <ø> (ø)	⬆️
superset/examples/sf_population_polygons.py	29.16% <ø> (ø)	⬆️
superset/examples/deck.py	11.11% <ø> (ø)	⬆️
superset/utils/dict_import_export.py	21.05% <ø> (ø)	⬆️
... and 71 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a199901...03f2d3c. Read the comment docs.

[villebro]

Nice work! LGTM, looks very clean. Just a few comments, mostly out of scope-stuff. @mistercrunch I propose including this in the 0.35 release, as these changes will most likely cause widespread conflicts when picking cherries for upcoming patch releases on the 0.35 branch.

[villebro]

LGTM. I will open a separate PR to address the out of scope comments.

[mistercrunch]

Confirmed with I can merge this, we're laying more refactors on top of this.