Use Python 3.7 for build

Author: dhalbert

.github/workflows/build.yml

@@ -18,10 +18,10 @@ jobs:
         awk -F '\/' '{ print tolower($2) }' |
         tr '_' '-'
         )
-    - name: Set up Python 3.6
+    - name: Set up Python 3.7
       uses: actions/setup-python@v1
       with:
-        python-version: 3.6
+        python-version: 3.7
     - name: Versions
       run: |
         python3 --version