Downloading mp3 does not work

[gitfortat]

When I try to download an mp3 (right-click) I get the following error (lines do not match with original version, since I made another commit, but this is unimportant):

Traceback (most recent call last):
File "/usr/lib/python3.5/site-packages/ldoce5viewer/qtgui/main.py", line 557, in finished
callback(reply.readAll())
File "/usr/lib/python3.5/site-packages/ldoce5viewer/qtgui/main.py", line 569, in showSaveDialog
file.write(data)
TypeError: write() argument must be str, not QByteArray

To fix it I changed the file mode to binary ("wb" instead of "w"): 08b27d8

Are the mp3 files not always in binary format? I am wondering why the default file mode seems to work for some. Are there different versions of the actual ldoce5 dictionary?