Hi!
lib/extras.py lines 123 and 128 refer to _cursor, but the class is inherited from DictCursorBase.
https://dndg.it/cgi-bin/gitweb.cgi?p=public/psycopg2.git;a=blob;f=lib/extras.py;h=2e3974b648bf10c76af8fdfbeb6add8aae3475a3;hb=HEAD#l123
--Regards,Alexey.