Use our own hypot() for older Python support

mosfet/path.py

@@ -1,7 +1,6 @@
 import importlib
 import functools
 import time
-from math import hypot, sqrt
 
 from astar import AStar
 
@@ -306,7 +305,7 @@ class Pathfinder(AStar):
     def distance_between(self, n1, n2):
         (x1, y1, z1) = n1
         (x2, y2, z2) = n2
-        return hypot(x2-x1, y2-y1, z2-z1)
+        return utils.hypot(x2-x1, y2-y1, z2-z1)
 
     def heuristic_cost_estimate(self, n1, n2):
         (x1, y1, z1) = n1