Update pr.yml

Change to python 3.8

Signed-off-by: Ming M Qin <38891913+MMelQin@users.noreply.github.com>

Author: MMelQin

.github/workflows/pr.yml

@@ -14,10 +14,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.7
+      - name: Set up Python 3.8
         uses: actions/setup-python@v2
         with:
-          python-version: "3.7"
+          python-version: "3.8"
       - name: Setup Dev Environment
         run: |
           pip install virtualenv