Exclude non-image types

[humitos]

Sometimes the application fails because it found a "Thumb.db" file, for example, and it is not an image. So, the application should exclude those file types don't supported by Flickr.

[jcohen]

Hiya,

I work at Flickr and we're seeing a fair number of failed uploads coming from users of your uploader for exactly this reason. If you could fix it to check that the file is a valid image before uploading, that'd be awesome! It looks like this should be relatively easy to do using the Pythong imghdr module: http://docs.python.org/library/imghdr.html.

Cheers,

Joshua