For XML serialization Tastypie requires this for XML serialization. Without it, XML serialization will crash with the message "`lxml` is required" but since we do have that installed, I went ahead and read their code and it is actually `defusedxml` that is required. An easy win for a PR against Tastypie but I'm about to sign off. Filed as toastdriven/django-tastypie#976

I had never heard of the library until now, but it is a security-hardened wrapper on lxml that was released earlier this year.