The ext2[34]-filesystem always has some amount for root user only to be able to do some maintance even if the user fills the partition.
You might want to analyze your optfs This list the largest folders of the /opt and /home folders. You might then ask how to proceed, remove the largest space wasters or 'simply' enlarge your optfs by shrinking your MyDocs partition following this wiki entry http://wiki.maemo.org/Repartitioning_the_flash
The most advanced method in this wiki is the solution using GParted.

The moving of python packages saved your rootfs to became full in the first place, later you installed some applications or copied some stuff to /home/user instead of MyDocs, may be.