The ornamental design for a rattantubcooler, as shown and described.
FIG. 1 is a perspective view of the rattan tub cooler showing my new design.
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is an opposite side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a perspective view of the rattan tub cooler wherein the lid is removed.
The rattan tub cooler has a rattan or faux rattan surface thereon. The features presented in broken lines are for environmental purposes only and form no part of the claimed design.