Edit the file: /etc/modules-load.d/cups-filters.conf
Make it look like this:
# Parallel printer driver modules loading for cups
# LOAD_LP_MODULE was 'yes' in /etc/default/cups
#lp
#ppdev
#parport_pc
Also, edit the file: /etc/default/cups
Make it look like this:
# do not load parallel port modules
LOAD_LP_MODULES="no"
Reboot your system, and the errors should be suppressed.