ci: upgrade Black to v20.8b1, drop Python 2.7/3.5, and disable check

Summary:
See #4406. Subsequent commits will re-run Black with the new settings
and new version (these commits will be ignored for blame purposes), and
then another commit will re-enable enforcement.

wchargin-branch: black-20x-no27-no35

Author: wchargin

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
         # flake8 should run on each Python version that we target,
         # because the errors and warnings can differ due to language
         # changes, and we want to catch them all.
-        python_version: ['3.5', '3.7']
+        python_version: ['3.6', '3.7']
     steps:
       - uses: actions/checkout@v1
       - uses: actions/setup-python@v1
@@ -65,7 +65,8 @@ jobs:
       - run: pip freeze --all
       - name: 'Lint Python code for style with Black'
         # You can run `black .` to fix all Black complaints.
-        run: black --check --diff .
+        # TODO(#4406): Re-enable this check.
+        run: black --check --diff . || true
 
   lint-rust:
     runs-on: ubuntu-16.04

pyproject.toml

@@ -1,5 +1,3 @@
 [tool.black]
 line-length = 80
-# TODO(@wchargin): Drop `py35` here once we drop support for Python 3.5
-# and aren't affected by <https://bugs.python.org/issue9232>.
-target-version = ["py27", "py35", "py36", "py37", "py38"]
+target-version = ["py36", "py37", "py38"]

tensorboard/pip_package/requirements_dev.txt

@@ -23,7 +23,7 @@ boto3==1.9.86
 moto==1.3.7
 
 # For linting
-black==19.10b0; python_version >= "3.6"
+black==20.8b1; python_version >= "3.6"
 flake8==3.7.8
 yamllint==1.17.0