Have Travis run mypy

Author: oschwald

.travis.yml

@@ -24,7 +24,7 @@ before_install:
   - sudo ldconfig
   - cd ..
   - pip install coverage coveralls
-  - if [[ $RUN_LINTER ]]; then pip install pylint black; fi
+  - if [[ $RUN_LINTER ]]; then pip install pylint black mypy; fi
   - |
     if [[ $RUN_SNYK && $SNYK_TOKEN ]]; then
       sudo apt-get install -y nodejs;
@@ -35,6 +35,7 @@ script:
   - if [[ $TRAVIS_PYTHON_VERSION != 'pypy' ]]; then export MM_FORCE_EXT_TESTS=1; fi
   - CFLAGS="-Werror -Wall -Wextra" coverage run --source maxminddb setup.py test
   - if [[ $RUN_SNYK && $SNYK_TOKEN ]]; then snyk test --org=maxmind --file=requirements.txt; fi
+  - if [[ $RUN_LINTER ]]; then mypy maxminddb tests; fi
   - if [[ $RUN_LINTER ]]; then pylint --rcfile .pylintrc maxminddb/*.py; fi
   - if [[ $RUN_LINTER ]]; then ./.travis-black.sh; fi