tower_notification creation error

[alanhuang281]

I followed official doc: https://docs.ansible.com/ansible/latest/modules/tower_notification_module.html#examples

trying to create a notification in awx by following the example code, but it always complains below issue: this looks like a bug ? does anyone experienced the same issue?
this is my ansible and tower ci version:
Package Version

---

ansible 2.8.4
ansible-lint 3.4.22

errors:
TASK [awx : Add PagerDuty notification] ****************************************************************************************************************************************************************************************************
task path: /etc/ansible/roles/awx/tasks/main.yml:281
<127.0.0.1> ESTABLISH LOCAL CONNECTION FOR USER: ah1000259263
<127.0.0.1> EXEC /bin/sh -c 'echo ~ah1000259263 && sleep 0'
<127.0.0.1> EXEC /bin/sh -c '( umask 77 && mkdir -p "echo /home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950" && echo ansible-tmp-1589527669.77-205649555478950="echo /home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950" ) && sleep 0'
Using module file /usr/lib/python2.7/site-packages/ansible/modules/web_infrastructure/ansible_tower/tower_notification.py
<127.0.0.1> PUT /home/ah1000259263/.ansible/tmp/ansible-local-2752Wq2t6x/tmpHwmb8k TO /home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py
<127.0.0.1> EXEC /bin/sh -c 'chmod u+x /home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/ /home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py && sleep 0'
<127.0.0.1> EXEC /bin/sh -c '/usr/bin/python2 /home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py && sleep 0'
<127.0.0.1> EXEC /bin/sh -c 'rm -f -r /home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/ > /dev/null 2>&1 && sleep 0'
The full traceback is:
Traceback (most recent call last):
File "/home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py", line 114, in
_ansiballz_main()
File "/home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py", line 106, in _ansiballz_main
invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)
File "/home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py", line 49, in invoke_module
imp.load_module('main', mod, module, MOD_DESC)
File "/tmp/ansible_tower_notification_payload_Llurry/main.py", line 393, in
File "/tmp/ansible_tower_notification_payload_Llurry/main.py", line 379, in main
File "/usr/lib/python2.7/site-packages/tower_cli/resources/notification_template.py", line 292, in modify
self.get(**copy.deepcopy(kwargs))
File "/usr/lib/python2.7/site-packages/tower_cli/resources/notification_template.py", line 414, in get
self._separate(kwargs)
File "/usr/lib/python2.7/site-packages/tower_cli/resources/notification_template.py", line 161, in _separate
data = json.loads(result[field])
File "/usr/lib64/python2.7/json/init.py", line 338, in loads
return _default_decoder.decode(s)
File "/usr/lib64/python2.7/json/decoder.py", line 366, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer

fatal: [localhost]: FAILED! => {
"changed": false,
"module_stderr": "Traceback (most recent call last):\n File "/home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py", line 114, in \n _ansiballz_main()\n File "/home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py", line 106, in _ansiballz_main\n invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)\n File "/home/ah1000259263/.ansible/tmp/ansible-tmp-1589527669.77-205649555478950/AnsiballZ_tower_notification.py", line 49, in invoke_module\n imp.load_module('main', mod, module, MOD_DESC)\n File "/tmp/ansible_tower_notification_payload_Llurry/main.py", line 393, in \n File "/tmp/ansible_tower_notification_payload_Llurry/main.py", line 379, in main\n File "/usr/lib/python2.7/site-packages/tower_cli/resources/notification_template.py", line 292, in modify\n self.get(**copy.deepcopy(kwargs))\n File "/usr/lib/python2.7/site-packages/tower_cli/resources/notification_template.py", line 414, in get\n self._separate(kwargs)\n File "/usr/lib/python2.7/site-packages/tower_cli/resources/notification_template.py", line 161, in _separate\n data = json.loads(result[field])\n File "/usr/lib64/python2.7/json/init.py", line 338, in loads\n return _default_decoder.decode(s)\n File "/usr/lib64/python2.7/json/decoder.py", line 366, in decode\n obj, end = self.raw_decode(s, idx=_w(s, 0).end())\nTypeError: expected string or buffer\n",
"module_stdout": "",
"msg": "MODULE FAILURE\nSee stdout/stderr for the exact error",
"rc": 1
}