The current update-manager code has this in file DistUpgrade/DistUpgradeCache.py, method checkFreeSpace. It now ignores any /proc/mounts lines it can't parse (that do not have exactly six space-delimited fields).
The current update-manager code has this in file DistUpgrade/ DistUpgradeCach e.py, method checkFreeSpace. It now ignores any /proc/mounts lines it can't parse (that do not have exactly six space-delimited fields).