cbtransfer failed to run on server with ipv6 address

[root@s10501-ip6 bin]# ./cbtransfer http://s10501-ip6.qe.couchbase.com:8091  /tmp/backup/ -u Administrator -p password 

Exception in thread w0:

Traceback (most recent call last):

  File "/usr/lib64/python2.7/threading.py", line 812, in __bootstrap_inner

    self.run()

  File "/usr/lib64/python2.7/threading.py", line 765, in run

    self.__target(*self.__args, **self.__kwargs)

  File "/opt/couchbase/lib/python/pump.py", line 345, in run_worker

    curx).run()

  File "/opt/couchbase/lib/python/pump.py", line 403, in run

    rv_batch, batch = self.source.provide_batch()

  File "/opt/couchbase/lib/python/pump_dcp.py", line 225, in provide_batch

    rv = self.get_dcp_conn()

  File "/opt/couchbase/lib/python/pump_dcp.py", line 486, in get_dcp_conn

    err, self.dcp_conn = pump.get_mcd_conn(host, port, username, password, bucket)

  File "/opt/couchbase/lib/python/pump.py", line 1106, in get_mcd_conn

    conn = cb_bin_client.MemcachedClient(host, port)

  File "/opt/couchbase/lib/python/cb_bin_client.py", line 45, in __init__

    self.s.connect_ex((host, port))

  File "/usr/lib64/python2.7/socket.py", line 224, in meth

    return getattr(self._sock,name)(*args)

gaierror: [Errno -2] Name or service not known

[root@s10501-ip6 bin]# ./cbtransfer  http://[fd63:6f75:6368:20d3:ac3c:257e:9c5:6619]:8091 /tmp/backup  -u Administrator -p password 

2017-12-29 16:05:59,384: mt "6f75" is not int, reset it to default port number

2017-12-29 16:05:59,405: mt "6f75" is not int, reset it to default port number

2017-12-29 16:05:59,406: mt "6f75" is not int, reset it to default port number

Exception in thread w0:

Traceback (most recent call last):

  File "/usr/lib64/python2.7/threading.py", line 812, in __bootstrap_inner

    self.run()

  File "/usr/lib64/python2.7/threading.py", line 765, in run

    self.__target(*self.__args, **self.__kwargs)

  File "/opt/couchbase/lib/python/pump.py", line 345, in run_worker

    curx).run()

  File "/opt/couchbase/lib/python/pump.py", line 403, in run

    rv_batch, batch = self.source.provide_batch()

  File "/opt/couchbase/lib/python/pump_dcp.py", line 225, in provide_batch

    rv = self.get_dcp_conn()

  File "/opt/couchbase/lib/python/pump_dcp.py", line 486, in get_dcp_conn

    err, self.dcp_conn = pump.get_mcd_conn(host, port, username, password, bucket)

  File "/opt/couchbase/lib/python/pump.py", line 1106, in get_mcd_conn

    conn = cb_bin_client.MemcachedClient(host, port)

  File "/opt/couchbase/lib/python/cb_bin_client.py", line 45, in __init__

    self.s.connect_ex((host, port))

  File "/usr/lib64/python2.7/socket.py", line 224, in meth

    return getattr(self._sock,name)(*args)

gaierror: [Errno -2] Name or service not known