fixup! f-strings are syntax errors in Python 3.5

.github/workflows/lint.yml

@@ -26,7 +26,15 @@ jobs:
           python -m pip install --upgrade pip
           pip install -e ".[all]"
       - name: Lint with flake8
+        if: python-version != "3.5"  # f-strings are syntax errors in Python 3.5
         run: |
           pip install flake8
           flake8 --ignore=E126,E127,E128,E131,E226,E231,E302,E303,E305,E401,E402,E701,E731,F401,F403,F405,W291,W292,W293,W391 \
                  --max-complexity=32 --max-line-length=525 --show-source --statistics .
+      - name: Lint with flake8 (Python 3.5)
+        if: python-version !== "3.5"  # f-strings are syntax errors in Python 3.5
+        run: |
+          pip install flake8
+          flake8 --ignore=E126,E127,E128,E131,E226,E231,E302,E303,E305,E401,E402,E701,E731,F401,F403,F405,W291,W292,W293,W391 \
+                 --max-complexity=32 --max-line-length=525 --show-source --statistics pywebio
+