Update circleci to run checkin tests on py3.8

[dsherry]

Support python 3.8

Fix #310

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After creating the pull request: in order to pass the changelog_updated check you will need to update the "Future Release" section of docs/source/changelog.rst to include this pull request by adding :pr:123.

[codecov]

Codecov Report

Merging #462 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #462      +/-   ##
==========================================
+ Coverage   98.25%   98.26%   +0.01%     
==========================================
  Files         104      104              
  Lines        3265     3292      +27     
==========================================
+ Hits         3208     3235      +27     
  Misses         57       57

Impacted Files	Coverage Δ
...onents/estimators/regressors/catboost_regressor.py	100% <0%> (ø)	⬆️
...ents/estimators/classifiers/catboost_classifier.py	100% <0%> (ø)	⬆️
evalml/tests/component_tests/test_components.py	100% <0%> (ø)	⬆️
evalml/tests/tuner_tests/test_skopt_tuner.py	100% <0%> (ø)	⬆️
evalml/tests/pipeline_tests/test_graphs.py	100% <0%> (ø)	⬆️
...ents/estimators/classifiers/logistic_regression.py	100% <0%> (ø)	⬆️
...mponents/estimators/regressors/linear_regressor.py	100% <0%> (ø)	⬆️
...s/components/estimators/regressors/rf_regressor.py	100% <0%> (ø)	⬆️
.../tests/automl_tests/test_auto_regression_search.py	100% <0%> (ø)	⬆️
...nents/estimators/classifiers/xgboost_classifier.py	100% <0%> (ø)	⬆️
... and 10 more

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[dsherry]

Wow, no checkin test errors! And no lint errors, which isn't what I expected. I guess we support python 3.8 now :)

[dsherry]

Not necessary but felt right

[angela97lin]

Wow, no errors? Sounds good true to be true (though I wonder what happened to that linting issue from a while ago...). 🚢

[jeremyliweishih]

👏

[dsherry]

@angela97lin yeah I know, I was surprised too! The linting issue may have had something to do with the isort version I had. I can't remember now. Was it just me who had the issue or did you have it too?

[angela97lin]

I'm still locally using 3.7.6 but when I tried 3.8.1 I had run into the same issues you did. :o