Can't save and reopen xlsx file with comments with version 2.3.0
*Created originally on Bitbucket by [SleepProgger](https://bitbucket.org/%7B5f47948d-0346-438c-ad58-81db466ada36%7D/)* I tried to load, change and save an xlsx file i downloaded from google spreadsheet and got this error on reloading the file: ``` #!python Traceback (most recent call last): File "D:\workspace\python\SantasImp\test.py", line 15, in <module> book = load_workbook(filename, keep_vba=True, data_only=True, guess_types=True) File "C:\Program Files (x86)\python\lib\site-packages\openpyxl\reader\excel.py", line 241, in load_workbook read_comments(new_ws, archive.read(comments_file)) File "C:\Program Files (x86)\python\lib\site-packages\openpyxl\reader\comments.py", line 31, in read_comments runtext = ''.join([t.text for t in run.findall('{%s}t' % SHEET_MAIN_NS)]) TypeError: sequence item 0: expected string, NoneType found ``` After some digging around i realized this happens when using comments. Removing the comments before saving solves this issue. Test case: ``` #!python filename = 'test.xlsx' book = load_workbook(filename, keep_vba=True) # clean comments sheet = book.active for row in sheet.rows: for cell in row: cell.comment = None book.save("test2.xlsx") filename = 'test2.xlsx' book = load_workbook(filename, keep_vba=True) ``` I added my test xlsx file generated by google spreadsheets. Thanks for this great piece of software, SleepProgger *Attachments:* [test.xlsx](/uploads/22d4f87219e5b8f40c646d529edfe3c9/test.xlsx)
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