Media Library rejects uploaded files if file has an uppercase extension

[Pi2048]

Steps to reproduce:

• Login and go to the Media Library
• Click 'Upload'
• Choose a file with a name that ends in '.JPG' (note the uppercase)
• Try to upload it

It yields an error about allowed extensions. However, .jpg is accepted. We should accept all upper-, lower- and mixed-case versions of extensions that we allow.

[Pi2048]

Seems to be a filebrowser(_safe) issue, submitted it there: https://github.com/stephenmcd/filebrowser-safe/issues/100.

[bartromgens]

This is indeed a issue in the mezzanine filebrowser version. Your suggestion to fix it seems the best way to go.

We can 'fix' it on our end by extending the FILEBROWSER_EXTENSIONS setting: https://github.com/jonge-democraten/website/blob/98a26686e46ab6ee8f13812c455e0a0b1e40f1c8/website/settings.py#L561 with upper case versions, but that is rather ugly work-around and still does not work for mixed upper and lower case extensions (although rare).

We can also fix the issue in filebrowser-safe and submit a PR if it is not handled in time, and it is easy to fix (the comment 'Lower case is important' is a bit strange). Might be a nice way to give something back.

[Pi2048]

This was apparently fixed in a more recent version of filebrowser_safe: https://github.com/stephenmcd/filebrowser-safe/commit/761421ff719b7b673d008dd4b65ba4ac242ecd7a. Let's upgrade and see whether the issue persists.