Comment 18 for bug 725408

While that alone wouldn't cause the error (it's guarded with a true), it is nonetheless quite strange:

Mar 20 22:48:25 ubuntu ubiquity: + mount -o ro /dev/mapper/nvidia_ahhfbbffp1 /tmp/tmp.FuQfIqOMOD
Mar 20 22:48:25 ubuntu ntfs-3g[6264]: Version 2010.8.8 external FUSE 28
Mar 20 22:48:25 ubuntu ntfs-3g[6264]: Mounted /dev/dm-2 (Read-Only, label "", NTFS 3.1)
Mar 20 22:48:25 ubuntu ntfs-3g[6264]: Cmdline options: ro
Mar 20 22:48:25 ubuntu ntfs-3g[6264]: Mount options: ro,allow_other,nonempty,relatime,fsname=/dev/dm-2,blkdev,blksize=4096
Mar 20 22:48:25 ubuntu ntfs-3g[6264]: Ownership and permissions disabled, configuration type 1
Mar 20 22:48:25 ubuntu ubiquity: +
Mar 20 22:48:25 ubuntu ubiquity: grep
Mar 20 22:48:25 ubuntu ubiquity: -s
Mar 20 22:48:25 ubuntu ubiquity: DISTRIB_ID
Mar 20 22:48:25 ubuntu ubiquity: /tmp/tmp.FuQfIqOMOD/etc/lsb-release
Mar 20 22:48:25 ubuntu ubiquity:
Mar 20 22:48:25 ubuntu ubiquity: + release=
Mar 20 22:48:25 ubuntu ubiquity: + true
Mar 20 22:48:25 ubuntu ubiquity: + umount /dev/mapper/nvidia_ahhfbbffp1
Mar 20 22:48:25 ubuntu ubiquity: umount: /dev/mapper/nvidia_ahhfbbffp1: not mounted
Mar 20 22:48:25 ubuntu ubiquity: + true

So it successfully mounted, but somewhere between that and the call to umount, when the only thing between them is a grep (that is also guarded with a true), it went away.