On py3 dict.keys() returns iterator instead of list:

    $ ./tzodb.py zhash
    Traceback (most recent call last):
      File "/home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/neo/t/./tzodb.py", line 141, in <module>
        main()
      File "/home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/neo/t/./tzodb.py", line 138, in main
        zhash()
      File "/home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/neo/t/./tzodb.py", line 59, in zhash
        optv, argv = getopt(sys.argv[2:], "h", ["help", "check=", "bench="] + hashRegistry.keys())
    TypeError: can only concatenate list (not "dict_keys") to list