Bump mypy version

Author: domdfcoding

.github/workflows/mypy.yml

@@ -40,7 +40,7 @@ jobs:
         if: steps.changes.outputs.code == 'true'
         uses: "actions/setup-python@v2"
         with:
-          python-version: "3.6"
+          python-version: "3.8"
 
       - name: Install dependencies 🔧
         run: |

tox.ini

@@ -77,11 +77,11 @@ deps = perflint
 commands = python3 -m perflint flake8_strftime {posargs}
 
 [testenv:mypy]
-basepython = python3.6
+basepython = python3.8
 ignore_errors = True
 changedir = {toxinidir}
 deps =
-    mypy==0.942
+    mypy==0.971
     -r{toxinidir}/tests/requirements.txt
 commands = mypy flake8_strftime tests {posargs}