ci: test on both py2 and py3

.github/workflows/tests.yml

@@ -40,7 +40,7 @@ jobs:
     - name: Run rule linter
       run: python scripts/lint.py rules/
 
-  tests:
+  tests27:
     runs-on: ubuntu-latest
     needs: [code_style, rule_linter]
     steps:
@@ -57,3 +57,20 @@ jobs:
     - name: Run tests
       run: pytest tests/
 
+  tests38:
+    runs-on: ubuntu-latest
+    needs: [code_style, rule_linter]
+    steps:
+    - name: Checkout capa with submodules
+      uses: actions/checkout@v2
+      with:
+        submodules: true
+    - name: Set up Python 3.8
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+    - name: Install capa
+      run: pip install -e .[dev]
+    - name: Run tests
+      run: pytest tests/
+