This bug was fixed in the package ubiquity - 2.18.2
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ubiquity (2.18.2) trusty; urgency=medium
* Set HOME, because without HOME GtkBuilder upon seeing a FileChooser
button in the ui file and trying to initialise object for it throws a
hizzy fit and aborts on an assert, if
** Also affects: ubiquity (Ubuntu)
Importance: Undecided
Status: New
** Changed in: ubiquity (Ubuntu)
Status: New = Confirmed
** Changed in: ubiquity (Ubuntu)
Importance: Undecided = High
** Changed in: ubiquity (Ubuntu)
Assignee: (unassigned) = Dimitri John Ledkov