The ornamental design for a messengerbag, as shown and described.
FIG. 1 is a front perspective view of a messenger bag showing my new design;
FIG. 2 is a front side view thereof;
FIG. 3 is a back side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top side view;
FIG. 7 is a bottom side view, and,
FIG. 8 is a front perspective view of the messenger bag in an open position.
The shading and surface pill-shaped detailing represent surface texture. The broken lines shown on the surface of the drawings represent stitching and are part of the claimed design.