Importing pictures from another libravatar instance is broken

The function get_context_data in the class ImportPhotoView from the ivatar/ivataraccount/views.py file generates a broken URL.

In this snippet the variable libravatar_service_url already contains an option at the end, namely '?d=404' :

libravatar_service_url = libravatar_url(
    email=addr,
    default=404,
)

A few lines later '?s=512' or '?s=80' is concatenated.