Using the following entries in the kickstart file part / --onpart sda5 part /boot --onpart sda1 part swap --onpart sda6 the following message occured during installation Exception Occured File "/usr/lib/anaconda/todo.py", line 395, in addMount self.mounts[location] = (device, fsystem, reformat) AttributeError: mounts
--onpart is know to have issues in 6.2. I will investigate your particular case.
Did you have a clearpart directive in your ks file? It won't generally work to have clearpart specified and try to use --onpart on a logical partition, since if any logical partitions preceeding the logical partition are removed then the numbering is all screwed up.
Please reopen this bug if you continue to have issues.