They're not the safest thing. They definitely aren't designed for high amp draw, but one light is going to use less than an amp.
OP, if you're looking for quick and easy, use one of those screw-in things. Personally, I'd do it right and remove the light, and install a box with an outlet. The wiring is already there, so all you'd have to do is remove the light, nail a plastic box on, pull the wire though, and attach it to an outlet. It would take about 15 minutes and cost less than a dollar for the box, outlet, and cover.