Error: One or more models did not validate:
invweb.connection: Accessor for field 's_port' clashes with related field 'Port.connection_set'. Add a related_name argument to the definition for 's_port'.
invweb.connection: Accessor for field 'd_port' clashes with related field 'Port.connection_set'. Add a related_name argument to the definition for 'd_port'.

class Port(models.Model):
        p_type = (
                ('RJ45', 'RJ45'),
        )
        device_id = models.ForeignKey(Device)
        port_type = models.CharField(max_length=5, choices=p_type, default='RJ45')

class Connection(models.Model):
        c_type = (
                ('Grey', 'Grey'),
                ('Orange', 'Orange')
        )
        s_port = models.ForeignKey(Port)
        d_port = models.ForeignKey(Port)
        color = models.CharField(max_length=10, choices=c_type, default='Grey')