Merged requested to merge bitbucket/merged-pr-16 into branch/2.1
Created originally on Bitbucket by evansd (Dave Evans)
Was already merged in Bitbucket before import, marked as merged by the import user
Sheet names are not escaped before being used to construct a regex in
Worksheet._unique_sheet_name. This means that sheet names such as "Test (" will cause it to break with an unbalanced parentheses error.