insane.bbclass: enhance gettext error message

Point the user at gettext.bbclass which handles adding the
correct gettext to DEPENDS.

Signed-off-by: Joshua Lock <josh@linux.intel.com>

meta/classes/insane.bbclass

@@ -510,5 +510,6 @@ Rerun configure task after fixing this. The path was '%s'""" % root)
           for config in configs:
               gnu = "grep \"^[[:space:]]*AM_GNU_GETTEXT\" %s >/dev/null" % config
               if os.system(gnu) == 0:
-                 bb.fatal("Gettext required but not in DEPENDS for file %s" % config)
+                 bb.fatal("Gettext required but not in DEPENDS for file %s.
+Missing inherit gettext?" % config)
 }