-k option is broken

[jvigne]

When the file is downloaded, its mime type is application/octet-stream instead of a csv mime type. This type is not included in CSV_CONTENT_TYPES. Therefore we get an error <sheet_id>.csv is not a csv.

Quick fix : add application/octet-stream to CSV_CONTENT_TYPES

[felginep]

In fact the -k option is not broken. The issue here is that we need to make sure Allow external access is on in sharing options.