'unnecessary-comprehension' warning is emitted when
unnecessary use of a comprehension is found.
classes attribute in Action can be a tuple,
so we need list() to ensure it is a list before adding 'disabled'.
I think it is time to introduce a method in Action class or somewhere
but it should be handled separately.
Change-Id: I16a98d56b6d0bd0af234b00735c6ed576620df7e