The current implementation of HierarchicalStringList allows the following:
FOO.bar = [
'foo',
'bar',
]
while
FOO.bar += [
'foo',
'bar',
]
would be invalid because of the StrictOrderingOnAppendList enforcement.
It also allows to overwrite the entire list with a subsequent
FOO.bar = [
'baz',
]
while we've explicitly forbidden such things for every other list.
While in the vicinity, fix HierarchicalStringList._get_export_variable to not
call the HierarchicalStringList constructor uselessly.
2a82df055d