TSP tutorial example of google's or-tools crashes - python-3.5

Question

The example program for TSP problems crashes on my machine (ubuntu 16.04) with the following message:
WARNING: Logging before InitGoogleLogging() is written to STDERR
F0430 14:40:29.424594 15961 search.cc:2658] Check failed: step > 0 (0 vs. 0)
*** Check failure stack trace: ***
Aborted (core dumped)
installed binary via pip3 install ortools
changed print statements for python 3
replaced pywrapcp.DefaultRoutingSearchParameters() with pywrapcp.RoutingModel.DefaultModelParameters()
The entire program, taken from https://developers.google.com/optimization/routing/tsp/tsp#program1, is below:
from ortools.constraint_solver import pywrapcp
from ortools.constraint_solver import routing_enums_pb2
# Distance callback
class CreateDistanceCallback(object):
"""Create callback to calculate distances between points."""
def __init__(self):
"""Array of distances between points."""
self.matrix = [
[ 0, 2451, 713, 1018, 1631, 1374, 2408, 213, 2571, 875, 1420, 2145, 1972], # New York
[2451, 0, 1745, 1524, 831, 1240, 959, 2596, 403, 1589, 1374, 357, 579], # Los Angeles
[ 713, 1745, 0, 355, 920, 803, 1737, 851, 1858, 262, 940, 1453, 1260], # Chicago
[1018, 1524, 355, 0, 700, 862, 1395, 1123, 1584, 466, 1056, 1280, 987], # Minneapolis
[1631, 831, 920, 700, 0, 663, 1021, 1769, 949, 796, 879, 586, 371], # Denver
[1374, 1240, 803, 862, 663, 0, 1681, 1551, 1765, 547, 225, 887, 999], # Dallas
[2408, 959, 1737, 1395, 1021, 1681, 0, 2493, 678, 1724, 1891, 1114, 701], # Seattle
[ 213, 2596, 851, 1123, 1769, 1551, 2493, 0, 2699, 1038, 1605, 2300, 2099], # Boston
[2571, 403, 1858, 1584, 949, 1765, 678, 2699, 0, 1744, 1645, 653, 600], # San Francisco
[ 875, 1589, 262, 466, 796, 547, 1724, 1038, 1744, 0, 679, 1272, 1162], # St. Louis
[1420, 1374, 940, 1056, 879, 225, 1891, 1605, 1645, 679, 0, 1017, 1200], # Houston
[2145, 357, 1453, 1280, 586, 887, 1114, 2300, 653, 1272, 1017, 0, 504], # Phoenix
[1972, 579, 1260, 987, 371, 999, 701, 2099, 600, 1162, 1200, 504, 0]] # Salt Lake City
def Distance(self, from_node, to_node):
return int(self.matrix[from_node][to_node])
def main():
# Cities
city_names = ["New York", "Los Angeles", "Chicago", "Minneapolis", "Denver", "Dallas", "Seattle",
"Boston", "San Francisco", "St. Louis", "Houston", "Phoenix", "Salt Lake City"]
tsp_size = len(city_names)
num_routes = 1 # The number of routes, which is 1 in the TSP.
# Nodes are indexed from 0 to tsp_size - 1. The depot is the starting node of the route.
depot = 0
# Create routing model
if tsp_size > 0:
routing = pywrapcp.RoutingModel(tsp_size, num_routes, depot)
search_parameters = pywrapcp.RoutingModel.DefaultModelParameters()
# Create the distance callback, which takes two arguments (the from and to node indices)
# and returns the distance between these nodes.
dist_between_nodes = CreateDistanceCallback()
dist_callback = dist_between_nodes.Distance
routing.SetArcCostEvaluatorOfAllVehicles(dist_callback)
# Solve, returns a solution if any.
assignment = routing.SolveWithParameters(search_parameters)
if assignment:
# Solution cost.
print("Total distance: {} miles".format(assignment.ObjectiveValue()))
# Inspect solution.
# Only one route here; otherwise iterate from 0 to routing.vehicles() - 1
route_number = 0
index = routing.Start(route_number) # Index of the variable for the starting node.
route = ''
while not routing.IsEnd(index):
# Convert variable indices to node indices in the displayed route.
route += str(city_names[routing.IndexToNode(index)]) + ' -> '
index = assignment.Value(routing.NextVar(index))
route += str(city_names[routing.IndexToNode(index)])
print("Route:\n\n{}".format(route))
else:
print('No solution found.')
else:
print('Specify an instance greater than 0.')
if __name__ == '__main__':
main()