The ornamental design for a junctionbox for catenarylight, as shown and described.
FIG. 1 is a perspective view of a junction box for catenary light, showing our new design;
FIG. 2 is a front elevation view thereof, the back view being a mirror image thereto;
FIG. 3 is a right side view thereof, the left side view being a mirror image thereto;
FIG. 4 is top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The shorter broken lines represent portions of the article that form no part of the claimed design. The longer broken lines represent environmental structure that forms no part of the claimed design.