fungi: This sudo kpartx -d /dev/loop4 is before trap_cleanup. I haven't found any other errors
```
2022-04-12 04:58:00.106 | INFO diskimage_builder.block_device.utils [-] Calling [sudo umount /var/cache/nodepool/dib_tmp/dib_build.OuW0QXUa/mnt/]
2022-04-12 04:58:00.666 | INFO diskimage_builder.block_device.utils [-] Calling [sudo kpartx -d /dev/loop4]
2022-04-12 04:58:00.713 | DEBUG diskimage_builder.block_device.utils [-] exec_sudo: device-mapper: remove ioctl on loop4p2  failed: Device or resource busy exec_sudo /usr/lib/python3.6/site-packages/diskimage_builder/block_device/utils.py:135
```