pytype: introduce configuration for running pytype

Install pytype and dependencies on Python 3.8 with:
  pip install --upgrade -r pytype_requirements.txt

Checks can then be run with:
  pytype

pytype_requirements.txt

@@ -0,0 +1,10 b''
+# Note: pytype currently only supports Python3.8
+pytype == 2021.1.8
+# optional modules that we want for pytype checking
+appenlight_client
+ipython
+kajiki
+psycopg2
+python-ldap
+python-pam
+tgext.debugbar

.hgignore

@@ -56,3 +56,4 b' syntax: regexp'
 ^deps\.dot$
 ^deps\.svg$
 ^deps\.txt$
+^\.pytype/

setup.cfg

@@ -35,3 +35,14 b' all_files = 1'
 
 [upload_sphinx]
 upload-dir = docs/_build/html
+
+[pytype]
+inputs =
+    kallithea
+    setup.py
+exclude =
+    **/test_*.py
+disable =
+    pyi-error
+keep_going = True
+#jobs = 3