Try to fix CI tests for Python 3.10

.github/workflows/run-tests.yml

@@ -10,7 +10,7 @@ jobs:
     timeout-minutes: 15
     strategy:
       matrix:
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9, "3.10"]
+        python-version: ["2.7", "3.5", "3.6", "3.7", "3.8", "3.9", "3.10"]
     steps:
       - uses: actions/checkout@v2
 
@@ -19,11 +19,18 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
 
-      - name: Install dependencies
+      - name: "Install dependencies (compatible)"
         run: |
           python -m pip install --upgrade pip
           # pytest 4.6.X works best for older Python versions
           pip install -U lxml "pytest==4.6.9" codecov 'coverage==4.5.4' pytest-cov
+        if: ${{ matrix.python-version == '2.7' }}
+
+      - name: "Install dependencies (up to date)"
+        run: |
+          python -m pip install --upgrade pip
+          pip install -U lxml pytest codecov coverage pytest-cov
+        if: ${{ matrix.python-version != '2.7' }}
 
       - run: py.test tests
         env: