fix mypy to max of 0.560 pending python/mypy#4563

Author: mattsb42-aws

tox.ini

@@ -63,31 +63,33 @@ commands =
         t.close()"
     coverage report -m
 
-[testenv:mypy-py3]
+[testenv:mypy-common]
 basepython = python3
 deps =
     coverage
-    mypy
+    mypy<=0.560
     mypy_extensions
     typing>=3.6.2
+
+[testenv:mypy-py3]
+basepython = {[testenv:mypy-common]basepython}
+deps = {[testenv:mypy-common]deps}
 commands =
     python -m mypy \
         --linecoverage-report build \
-        src/dynamodb_encryption_sdk/
+        src/dynamodb_encryption_sdk/ \
+        {posargs}
     {[testenv:mypy-coverage]commands}
 
 [testenv:mypy-py2]
-basepython = python3
-deps =
-    coverage
-    mypy
-    mypy_extensions
-    typing>=3.6.2
+basepython = {[testenv:mypy-common]basepython}
+deps = {[testenv:mypy-common]deps}
 commands =
     python -m mypy \
         --py2 \
         --linecoverage-report build \
-        src/dynamodb_encryption_sdk/
+        src/dynamodb_encryption_sdk/ \
+        {posargs}
     {[testenv:mypy-coverage]commands}
 
 # Linters