Cannot mount disk image in sandbox

Summary

When creating disk images it is sometimes necessary to mount the image, for example installing systemd-boot seems to require the image to be mounted, but you can't use the mount command in the sandbox, as it requires root access. I don't doubt this could prove a difficulty in other cases during the construction of disk images.

Steps to reproduce

• Create/import a disk image
• Attempt to mount said image

I hit this issue while trying to switch to systemd-boot for the freedesktop-sdk bootable images.

What is the current bug behavior?

Fails with PermissionError

What is the expected correct behavior?

Disk image is mounted successfully.