Unlike Python 2, in Python 3 strings also have attribute '__iter__'.
Because of that, a string could be passed to select_file(), that
actually expects a list as the first parameter.
P.S. Madness, Python 3 is just a new different language...
P.P.S. They should have renamed it not to confuse people.
Change-Id: I92af47abb6adff0271c55e7f278e8c5188f2be75
Fixes: OS#4419