Add mypy CI job

.travis.yml

@@ -18,6 +18,9 @@ branches:
 matrix:
   fast_finish: true
   include:
+    - python: 3.6
+      env:
+        - TOXENV=mypy
     - python: 3.6
       env:
         - TOXENV=py36-cov,package_readme

dev-requirements.txt

@@ -2,3 +2,4 @@ pytest>=3.0
 tox>=2.5
 bump2version>=0.5.6
 sphinx>=1.5.5
+mypy

mypy.ini

@@ -0,0 +1,21 @@
+[mypy]
+python_version = 3.6
+files = Lib/fontTools/misc/plistlib
+follow_imports = silent
+ignore_missing_imports = True
+warn_redundant_casts = True
+warn_unused_configs = True
+warn_unused_ignores = True
+
+[mypy-fontTools.misc.plistlib]
+check_untyped_defs = True
+disallow_any_generics = True
+disallow_incomplete_defs = True
+disallow_subclassing_any = True
+disallow_untyped_decorators = True
+disallow_untyped_calls = False
+disallow_untyped_defs = True
+no_implicit_optional = True
+no_implicit_reexport = True
+strict_equality = True
+warn_return_any = True

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 3.0
-envlist = py3{6,7,8}-cov, htmlcov
+envlist = mypy, py3{6,7,8}-cov, htmlcov
 skip_missing_interpreters=true
 
 [testenv]
@@ -33,6 +33,13 @@ commands =
     coverage combine
     coverage html
 
+[testenv:mypy]
+deps =
+    -r dev-requirements.txt
+skip_install = true
+commands =
+    mypy
+
 [testenv:codecov]
 passenv = *
 deps =