sing - minor, respond with actual API error on failure, rather than just always "Not found!"

cogs/sing.py

@@ -78,7 +78,9 @@ class Sing(commands.Cog):
                     return
                 
                 if len(search_result) == 1:
-                    return await ctx.respond("ERR: Not found!")
+                    # Error response from API
+                    error, *_ = search_result[0]
+                    return await ctx.respond(error)
                 if not isinstance(search_result[0], tuple):
                     return # Invalid data type
                 (