Finish up MyPy type checking. While there, refactor a bit.

test/mypy.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+_cdir=$(cd -- "$(dirname "$0")" && pwd)
+command -v mypy > /dev/null 2>&1
+if [ $? -ne 0 ]; then
+	echo "err: mypy (Optional Static Typing for Python) not found."
+	exit 1
+fi
+for _pyver in 2.7 3.7; do
+	echo "--- Python ${_pyver}"
+	mypy --no-error-summary --strict --warn-unreachable --python-version "${_pyver}" "${_cdir}/../gp-okta.py"
+done