Feature Request: OS updater to check space in /opt

The Sailfish OS updater is already very good at checking some conditions (e.g.: incompatible application that could cause problem and might require deinstallation before updating, free space on root device, etc.)

It would be great if future versions could also check the free space available on the /opt partition ?

Use case:

Some users are likely to keep both the new patched system.img and the original system.img, just in case (I certainly do).

Under those circumstances, the space left isn’t enough, and attempting to upgrade package aliendalvik-system fails which leads to the os upgrade failing.