Comment 0 for bug 1462139

Here's the relevant part of the curtin output:

Installing for i386-pc platform.
Installation finished. No error reported.
umount: /tmp/tmpM4R1dI/target/dev: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
Unexpected error while running command.
Command: ['umount', '/tmp/tmpM4R1dI/target/dev']
Exit code: 1
Reason: -
Stdout: ''
Stderr: ''
Installation failed with exception: Unexpected error while running command.
Command: ['curtin', 'curthooks']

I spoke with Scott Moser on IRC about this, and he suggested the attached patch, which fixed the problem 100%.

I checked the installation output of a few of my MAAS nodes, and didn't see any lsof output. So I assume the "udevadm settle" command is the fix.

(Thanks Scott! I hope we can land this in time for MAAS 1.8.)