GHA: Simplify and update lint.yml

.github/workflows/lint.yml

@@ -4,39 +4,34 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
-    strategy:
-      matrix:
-        python-version: [3.8]
 
     steps:
       - uses: actions/checkout@v2
 
-      - name: pip cache
+      - name: Cache
-        uses: actions/cache@v1
+        uses: actions/cache@v2
         with:
-          path: ~/.cache/pip
+          path: |
-          key: lint-pip-${{ hashFiles('**/setup.py') }}
+            ~/.cache/pip
+            ~/.cache/pre-commit
+          key:
+            lint-v2-${{ hashFiles('**/setup.py') }}-${{
+            hashFiles('**/.pre-commit-config.yaml') }}
           restore-keys: |
-            lint-pip-
+            lint-v2-
 
-      - name: pre-commit cache
+      - name: Set up Python
-        uses: actions/cache@v1
+        uses: actions/setup-python@v2
         with:
-          path: ~/.cache/pre-commit
+          python-version: 3.8
-          key: lint-pre-commit-v1-${{ hashFiles('**/.pre-commit-config.yaml') }}
-          restore-keys: |
-            lint-pre-commit-v1-
-
-      - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v1
-        with:
-          python-version: ${{ matrix.python-version }}
 
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
+          python -m pip install -U pip
-          python -m pip install --upgrade tox
+          python -m pip install -U tox
 
       - name: Lint
         run: tox -e lint
+        env:
+          PRE_COMMIT_COLOR: always