Openpyxl corrupts Excel 2010 *.xlsx file
*Created originally on Bitbucket by [seroy (Roman Selivanov)](https://bitbucket.org/%7Baff44650-1993-437d-8717-0dcbf1b1d496%7D/)*
File was created in Excel 2010, when i try use openpyxl (2.4.8) for generate something on it base i get "unreadable content" error message in Excel. Even without any modification:
```
#!python
wb = load_workbook('invoice.xlsx')
response = HttpResponse(content_type='application/vnd.ms-excel')
response.write(save_virtual_workbook(wb))
```
I get error in Excel:
"Excel found unreadable content in 'invoice.xlsx'. Do you want to recover teh contents of this workbook? If you trust the source of this workbook, click Yes. (Yes) (No)"
*Attachments:* [invoice.xlsx](/uploads/6d5c87dad865b5391f0a974bd6d260ac/invoice.xlsx)
issue