Move black testing definition as part of pre-commit.

For this to work, the black command line options need to be replaced with a
pyproject.toml file defining the settings, that can be reused.

.github/workflows/build.yml

@@ -42,25 +42,19 @@ jobs:
       # (e.g. - apt-get: gettext, etc; pip: circuitpython-build-tools, requirements.txt; etc.)
       run: |
         source actions-ci/install.sh
-    - name: Pip install pylint, black, Sphinx, pre-commit
+    - name: Pip install pylint, Sphinx, pre-commit
       run: |
-        pip install --force-reinstall pylint black==19.10b0 Sphinx sphinx-rtd-theme pre-commit
+        pip install --force-reinstall pylint Sphinx sphinx-rtd-theme pre-commit
     - name: Library version
       run: git describe --dirty --always --tags
     - name: Pre-commit hooks
       run: |
         pre-commit install
         pre-commit run --all-files
-    - name: Check formatting
-      run: |
-        black --check --target-version=py35 .
     - name: PyLint
       run: |
         pylint $( find . -path './adafruit*.py' )
         ([[ ! -d "examples" ]] || pylint --disable=missing-docstring,invalid-name,bad-whitespace $( find . -path "./examples/*.py" ))
-    - name: Check formatting
-      run: |
-        black --check --target-version=py35 .
     - name: Build assets
       run: circuitpython-build-bundles --filename_prefix ${{ steps.repo-name.outputs.repo-name }} --library_location .
     - name: Build docs

.pre-commit-config.yaml

@@ -3,6 +3,10 @@
 # SPDX-License-Identifier: Unlicense
 
 repos:
+-   repo: https://github.com/python/black
+    rev: 19.10b0
+    hooks:
+    - id: black
 -   repo: https://github.com/fsfe/reuse-tool
     rev: latest
     hooks:

pyproject.toml

@@ -0,0 +1,6 @@
+# SPDX-FileCopyrightText: 2020 Diego Elio Pettenò
+#
+# SPDX-License-Identifier: Unlicense
+
+[tool.black]
+target-version = ['py35']