Update HTMLTidy.yml

Author: guwirth

.github/workflows/HTMLTidy.yml

@@ -15,6 +15,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.x'
     - name: Install HTML Tidy
       run: |
          wget https://github.com/htacg/tidy-html5/releases/download/5.8.0/tidy-5.8.0-Linux-64bit.deb