Created originally on Bitbucket by jamesbroadhead
Was already merged in Bitbucket before import, marked as merged by the import user
This adds an explicit regression test for https://bitbucket.org/openpyxl/openpyxl/issue/433 following the fix here https://bitbucket.org/openpyxl/openpyxl/commits/488b1ff05e4c9634f2b8230d5da6a31bc471b291