Without solving the actual issue, you might get the desired result by installing erp5 from a debian package as discussed on http://erp5solutions.blogspot.nl/2013/01/install-erp5-using-rpmdeb-for-end-users.html.
I did recently successfully install ERP5 trough slapos on an Ubuntu laptop and on a debian VM following the tutorials of the OSOE project.
Bert