T0ha/ezodf — pull request #3 by kenchou (2014-08-27 07:15:20+00:00)
Title: support google spreadsheet export *.ods

load an .ods file that export from google spreadsheet is broken.
TypeError: Argument must be bytes or unicode, got 'NoneType'
```
Traceback (most recent call last):
File "./import_diff.py", line 405, in
doc = ezodf.opendoc(data_filename)
File "/Library/Python/2.7/site-packages/ezodf/document.py", line 49, in opendoc
return PackagedDocument(filemanager=fm, mimetype=mimetype)
File "/Library/Python/2.7/site-packages/ezodf/document.py", line 191, in __init__
self.filemanager.manifest.add('/', mimetype)
File "/Library/Python/2.7/site-packages/ezodf/manifest.py", line 40, in add
set_media_type_and_version(file_entry)
File "/Library/Python/2.7/site-packages/ezodf/manifest.py", line 33, in set_media_type_and_version
file_entry.set(CN('manifest:media-type'), media_type)
File "lxml.etree.pyx", line 713, in lxml.etree._Element.set (src/lxml/lxml.etree.c:39488)
File "apihelpers.pxi", line 520, in lxml.etree._setAttributeValue (src/lxml/lxml.etree.c:17682)
File "apihelpers.pxi", line 1331, in lxml.etree._utf8 (src/lxml/lxml.etree.c:24677)
TypeError: Argument must be bytes or unicode, got 'NoneType'
```