Begin work on Python2 support

.github/workflows/main.yml

@@ -34,8 +34,16 @@ jobs:
         run: |
           # Require cryptography >= 3.1 because in 3.0 and below, the backend param in load_key_and_certificates was still required.
           pip3 install freezegun lxml pycryptodome rsa oscrypto "cryptography>=3.1"
+          # Install Python2 stuff
+          curl https://bootstrap.pypa.io/pip/2.7/get-pip.py --output get-pip.py
+          python2 get-pip.py
+          pip2 install freezegun mock lxml pycryptodome "rsa<=4.3" oscrypto cryptography==3.1
 
-      - name: Run tests
+      - name: Run tests (Python 3)
         run: |
-          cd tests && ./main.py
+          cd tests && python3 ./main.py && cd ..
+
+      - name: Run tests (Python 2)
+        run: |
+          cd tests && PYTHONWARNINGS=ignore python2 ./main.py && cd ..