mime type macro error with an xslm file

Created originally on Bitbucket by ptitjano

Hi, The following code produces an error with both version 2.3.5 (from archlinux package) or 2.4 from pip using python 2.7 or 3.5:

#!python

wb = load_workbook('Analyse des maitrise.xlsm', keep_vba=True)
ws = wb.get_sheet_by_name('chefs')
ws.cell(column=1, row=1, value=3.14)
wb.save('new_document.xlsm')

#!python

wb.save('new_document.xlsm')
  File "/usr/lib/python2.7/site-packages/openpyxl/workbook/workbook.py", line 339, in save
    save_workbook(self, filename)
  File "/usr/lib/python2.7/site-packages/openpyxl/writer/excel.py", line 268, in save_workbook
    writer.save(filename)
  File "/usr/lib/python2.7/site-packages/openpyxl/writer/excel.py", line 250, in save
    self.write_data()
  File "/usr/lib/python2.7/site-packages/openpyxl/writer/excel.py", line 98, in write_data
    self.manifest._write(archive, self.workbook)
  File "/usr/lib/python2.7/site-packages/openpyxl/packaging/manifest.py", line 167, in _write
    archive.writestr(self.path, tostring(self.to_tree()))
  File "/usr/lib/python2.7/site-packages/openpyxl/packaging/manifest.py", line 124, in to_tree
    for ext, mime in self.extensions:
  File "/usr/lib/python2.7/site-packages/openpyxl/packaging/manifest.py", line 116, in extensions
    return [(ext[1:], mimetypes.types_map[ext]) for ext in sorted(exts)]
KeyError: ''

Attachments: Analyse_des_maitrise.xlsm