fixed the error

backend/src/utils/optimizer.py

@@ -487,7 +487,7 @@ class Optimizer:
 
         # Raise error if no solution is found
         if not res.success :
-            raise ArithmeticError("No solution could be found, the problem is overconstrained. Please adapt your must_dos")
+            raise ArithmeticError("No solution could be found, the problem is overconstrained. Try with a longer trip (>30 minutes).")
 
         # If there is a solution, we're good to go, just check for connectiveness
         order, circles = self.is_connected(res.x)