test/check_exercises.py: improve portability (#1626)
test/check_exercises.py: improve portability (#1626)

Closes #1625
jmluy/xpython,jmluy/xpython,N-Parsons/exercism-python,N-Parsons/exercism-python,behrtam/xpython,exercism/xpython,smalley/python,behrtam/xpython,exercism/python,smalley/python,exercism/xpython,exercism/python