I have [[fa:foo]] and [[en:foo]] both of them doesn't have Item at wikidata. interwikidata.py couldn't create new item and add these two links to it.
for example at here these pages have link to enwiki bot the bot couldn't add the to wikidata.
I checked it's code at try_to_add it returns False for some case so at line 94 we should have this code
if self.getOption('create') and (item is None or item is False):