isogram: test with duplicate letter and nonletter character (#513)
isogram: test with duplicate letter and nonletter character (#513)

test with duplicate letter and nonletter character

exercism/python,behrtam/xpython,pheanex/xpython,exercism/xpython,jmluy/xpython,pheanex/xpython,behrtam/xpython,mweb/python,exercism/python,N-Parsons/exercism-python,N-Parsons/exercism-python,jmluy/xpython,smalley/python,smalley/python,exercism/xpython,mweb/python