[CI] Lint stage is added.

Do not run tests if lint fails.

Author: dmitry-lipetsk

.github/workflows/package-verification.yml

@@ -10,9 +10,31 @@ on:
     branches: [ "master" ]
 
 jobs:
-  build:
+  lint:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v3
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        python -m pip install flake8 flake8-pyproject
+    - name: Lint with flake8
+      run: |
+        flake8 .
 
+  test:
     runs-on: ubuntu-latest
+    needs: lint
     strategy:
       fail-fast: false
       matrix: