Try installing Python myself

Author: brandon-rhodes

.github/workflows/ci.yml

@@ -18,12 +18,14 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python
-      uses: actions/setup-python@v2
-      with:
-        python-version: 3.6.15
+      run:
+        apt update
+        apt install -y -y -q -q python3-pip
+        virtualenv V
 
     - name: Install pinned dependencies
       run: |
+        source ./V/bin/activate
         python -m pip install --upgrade pip
         pip install astropy==3.0.1 docutils==0.17.1 matplotlib==3.3.0 numpy==1.15.4 pandas==1.0.0 pyflakes scipy==1.2.2 sphinx==1.7.2 spktype21