TypeError: 'NoneType' object has no attribute '__getitem__'

Run VMTP:

# vmtp -d -c vmtp.cfg -r admin-openrc.sh -p admin --protocol T --json test44.json

Output:
2016-11-11 14:49:52,612 WARNING Invalid public_key_file:/tmp/ssh/id_rsa.pub
2016-11-11 14:49:52,612 WARNING Invalid private_key_file:/tmp/ssh/id_rsa
2016-11-11 14:49:52,613 INFO Using http://172.16.xx.xx:5000/v2.0
2016-11-11 14:49:52,613 INFO VM public key: /root/.ssh/id_rsa.pub
2016-11-11 14:49:52,613 INFO VM private key: /root/.ssh/id_rsa
2016-11-11 14:49:54,151 INFO Found image ubuntu14.04 to launch VM, will continue
/root/vmtpenv/lib/python2.7/site-packages/keystoneclient/service_catalog.py:200: UserWarning: Providing attr without filter_value to get_urls() is deprecated as of the 1.7.0 release and may be removed in the 2.0.0 release. Either both should be provided or neither should be provided.
  'Providing attr without filter_value to get_urls() is '
2016-11-11 14:49:54,671 WARNING No external network found.
2016-11-11 14:49:55,441 INFO Created internal network: pns-internal-net.
2016-11-11 14:49:56,940 INFO Created internal network: pns-internal-net2.
2016-11-11 14:49:56,992 INFO OpenStack agent: Open vSwitch agent
2016-11-11 14:49:56,992 INFO OpenStack network type: vxlan
2016-11-11 14:49:59,349 INFO [TestServer1] Creating server VM...
2016-11-11 14:49:59,349 DEBUG [TestServer1] Starting on zone nova:localhost.localdomain
2016-11-11 14:50:01,523 DEBUG [TestServer1] VM status=BUILD, retrying 1 of 50...
2016-11-11 14:50:03,771 DEBUG [TestServer1] VM status=BUILD, retrying 2 of 50...
2016-11-11 14:50:06,018 DEBUG [TestServer1] VM status=BUILD, retrying 3 of 50...
2016-11-11 14:50:08,264 DEBUG [TestServer1] VM status=BUILD, retrying 4 of 50...
2016-11-11 14:50:10,493 ERROR Traceback (most recent call last):
  File "/root/vmtpenv/lib/python2.7/site-packages/vmtp/vmtp.py", line 426, in run
    self.setup()
  File "/root/vmtpenv/lib/python2.7/site-packages/vmtp/vmtp.py", line 301, in setup
    self.net.vm_int_net[0])
  File "/root/vmtpenv/lib/python2.7/site-packages/vmtp/vmtp.py", line 161, in create_instance
    init_file_name=user_data_file))
  File "/root/vmtpenv/lib/python2.7/site-packages/vmtp/perf_instance.py", line 47, in create
    init_file_name)
  File "/root/vmtpenv/lib/python2.7/site-packages/vmtp/instance.py", line 189, in create
    fip = self.net.create_floating_ip()
  File "/root/vmtpenv/lib/python2.7/site-packages/vmtp/network.py", line 329, in create_floating_ip
    "floating_network_id": self.ext_net['id']
TypeError: 'NoneType' object has no attribute '__getitem__'

Other info
OpenStack Version：Mitaka
Python Version：2.7.5
OS：CentOS 7.2

admin-openrc.sh file
# cat admin-openrc.sh
unset OS_SERVICE_TOKEN
export OS_USERNAME=admin
export OS_PASSWORD=admin
export OS_AUTH_URL=http://172.16.xx.xx:5000/v2.0
export PS1='[\u@\h \W(keystone_admin)]\$ '
export OS_TENANT_NAME=admin
export OS_REGION_NAME=RegionOne