Comment 1 for bug 1520377

Results so far:

My bash prompt sets the window title to the tty number, a unique number for each terminal at a time. I'm testing by starting up Terminator, then pressing Ctrl+Shift+T, Ctrl+Shift+E, Ctrl+D.

paned.py -> wrapcloseterm(), "At this point we only have one child, which is the surviving term". Notebook's vpaned or hpaned child is removed and we're about to add the terminal directly as the new child. Hence "parent.add(sibling, metadata)" is called.

metadata, for some reason, contains the title of the tab that's being removed.

notebook.py -> add(), calls newtab() in turn. Due to metadata['label'] being defined, calls label.set_custom_label() in turn. Things obviously go wrong from this point.