The Bill Invoice importer is an optional module and needs to enabled by editing the file $HOME/.gnucash/config.user, adding the line:

(gnc:module-load "gnucash/plugins/bi_import" 0)

The example csv file must have the 22 elements for it to work.

To use the example file, create an account "Expenses:Materials General" and a Customer with owner = 000013.

More information can be found at http://svn.gnucash.org/docs/guide/python-import-invoices.html