malloc: *** error in re for Python 3.5

re.scanner_crash.py

import re

def fn():
    scanner = re.Scanner([
        (r'([0-9]{2}):([0-9]{2}):([0-9]{2})', lambda y, x: x),
        (r'.', lambda y, x: x)
    ])
    return scanner.scan("10:10:10")

# This works on Python 2.7, but not on Python 3.5
for i in range(10):
    print(fn())
    
# Error: Python(87764,0x7fff72029000) malloc: *** error for object 0x10331d4e8: incorrect checksum for freed object - object was probably modified after being freed.