[Django]-Cannot convert dictionary update sequence element #0 to a sequence

I found the error. In my context_processors.py file, I had :

def cached_queries(request):
    return {'query_lastname', cache.get('query_lastname')}

instead of

def cached_queries(request):
    return {'query_lastname' : cache.get('query_lastname')}

Now it seems work so I apologize for this silly question …