Update run-unit-tests.yml

Moved python 3.6 to its own job since it does not run on 'ubunto-latest'. See ongoing issue: actions/setup-python#544

Author: pelaezryan

.github/workflows/run-unit-tests.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9, "3.10"]
+        python-version: [3.7, 3.8, 3.9, "3.10"]
         os: [ubuntu-latest, macOS-latest, windows-latest ]
 
     steps:
@@ -33,3 +33,26 @@ jobs:
     - name: Test with pytest
       run: |
         pytest
+        
+  build-python-legacy:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: [3.6]
+        os: [ubuntu-20.04, macOS-latest, windows-latest ]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements.txt
+        pip install -r test_requirements.txt
+    - name: Test with pytest
+      run: |
+        pytest