Use mypy for static typing job

I prefer pytype's approach, but pytype doesn't support Python 3.8 or 3.9
yet, which is unnecessarily restrictive. ☹

Author: pganssle

.github/workflows/tests.yml

@@ -31,7 +31,7 @@ jobs:
     runs-on: "ubuntu-latest"
     strategy:
       matrix:
-        toxenv: ["build", "precommit", "pytype", "docs"]
+        toxenv: ["build", "precommit", "typing", "docs"]
     env:
       TOXENV: ${{ matrix.toxenv }}
 

bump_version.py

@@ -2,7 +2,7 @@
 import io
 import pathlib
 
-import parver
+import parver  # type: ignore
 
 REPO_ROOT = pathlib.Path(__file__).parent
 VERSION = REPO_ROOT / pathlib.Path("VERSION")

tox.ini

@@ -38,16 +38,15 @@ deps =
 commands =
     python bump_version.py {posargs}
 
-[testenv:pytype]
+[testenv:typing]
 description = Run typechecking
-basepython = python3.7
 skip_install = True
 deps =
-    pytype
+    mypy
     parver
 commands =
-    pytype {posargs} update.py
-    pytype {posargs} bump_version.py
+    mypy {posargs} update.py
+    mypy {posargs} bump_version.py
 
 [testenv:format]
 description = Run auto formatters