XML error in generated xlsx file after using page break in worksheets with charts

Created originally on Bitbucket by liuyuqian

Use line chart demo code, then add a page break. Generated xlsx file can be read with WPS or LibreOffice,and page break work well,but raise a XML error after Excel 2010 & 2016 fixed the file.

Environment:Python 3.5 openpyxl 2.4.1 Excel 2010 & 2016

Attachments: linecharts.py line.xlsx

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information