django.core.files.storage.base.Storage.get_availabe_name and get_alternative_name assumes that filenames contain only one dot: the dot of the extenstion.

[Abdulelah Taher]

If I have a file named 'a.b.pdf'
then get_alternative_name would return 'a_{random}.b.pdf'
which is not correct.
the random string should between the filename and the actual extension: 'a.b_{random}.pdf'.