[lint] run mypy on each CI run

Author: jlaine

.github/workflows/tests.yml

@@ -12,12 +12,13 @@ jobs:
         with:
           python-version: 3.7
       - name: Install packages
-        run: pip install black flake8 isort mypy
+        run: pip install black flake8 isort mypy types-certifi types-cryptography types-pyopenssl
       - name: Run linters
         run: |
           flake8 examples src tests
           isort --check-only --diff examples src tests
           black --check --diff examples src tests
+          mypy src tests
 
   test:
     runs-on: ${{ matrix.os }}

tests/utils.py

@@ -73,7 +73,7 @@ def generate_ed448_certificate(common_name, alternative_names=[]):
     )
 
 
-def load(name):
+def load(name: str) -> bytes:
     path = os.path.join(os.path.dirname(__file__), name)
     with open(path, "rb") as fp:
         return fp.read()