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##### SUMMARY
With addition of OAuthClient in snow_* modules, I am getting following error - 
```
Traceback (most recent call last):
  File "/Users/akasurde/.ansible/tmp/ansible-tmp-1563543375.7458959-114877035679906/AnsiballZ_snow_record.py", line 125, in <module>
    _ansiballz_main()
  File "/Users/akasurde/.ansible/tmp/ansible-tmp-1563543375.7458959-114877035679906/AnsiballZ_snow_record.py", line 117, in _ansiballz_main
    invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)
  File "/Users/akasurde/.ansible/tmp/ansible-tmp-1563543375.7458959-114877035679906/AnsiballZ_snow_record.py", line 51, in invoke_module
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/tmp/ansible_snow_record_payload_brr2thzt/__main__.py", line 339, in <module>
  File "/tmp/ansible_snow_record_payload_brr2thzt/__main__.py", line 335, in main
  File "/tmp/ansible_snow_record_payload_brr2thzt/__main__.py", line 205, in run_module
  File "/tmp/ansible_snow_record_payload_brr2thzt/ansible_snow_record_payload.zip/ansible/module_utils/service_now.py", line 57, in login
AttributeError: 'NoneType' object has no attribute 'generate_token'
```

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
2.9
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
Nothing specific
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
MacOS Mojave

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml
---
- hosts: localhost
  tasks:
    - snow_record:
        instance: "instance_id"
        password: "password"
        username: admin
        data:
          short_description: "Description"
          priority: 2
        state: present
```

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##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
Playbook should be successful.

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below
Traceback (most recent call last):
  File "/Users/akasurde/.ansible/tmp/ansible-tmp-1563543375.7458959-114877035679906/AnsiballZ_snow_record.py", line 125, in <module>
    _ansiballz_main()
  File "/Users/akasurde/.ansible/tmp/ansible-tmp-1563543375.7458959-114877035679906/AnsiballZ_snow_record.py", line 117, in _ansiballz_main
    invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)
  File "/Users/akasurde/.ansible/tmp/ansible-tmp-1563543375.7458959-114877035679906/AnsiballZ_snow_record.py", line 51, in invoke_module
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/tmp/ansible_snow_record_payload_brr2thzt/__main__.py", line 339, in <module>
  File "/tmp/ansible_snow_record_payload_brr2thzt/__main__.py", line 335, in main
  File "/tmp/ansible_snow_record_payload_brr2thzt/__main__.py", line 205, in run_module
  File "/tmp/ansible_snow_record_payload_brr2thzt/ansible_snow_record_payload.zip/ansible/module_utils/service_now.py", line 57, in login
AttributeError: 'NoneType' object has no attribute 'generate_token'
```

from __future__ import absolute_import, division, print_function
__metaclass__ = type
import traceback
from ansible.module_utils.basic import missing_required_lib
HAS_PYSNOW = False
PYSNOW_IMP_ERR = None
try:
    import pysnow
    HAS_PYSNOW = True
except ImportError:
    PYSNOW_IMP_ERR = traceback.format_exc()
class ServiceNowClient(object):
    def __init__(self, module):
        """
        Constructor
        """
        if not HAS_PYSNOW:
            module.fail_json(msg=missing_required_lib('pysnow'), exception=PYSNOW_IMP_ERR)
        self.module = module
        self.params = module.params
        self.client_id = self.params['client_id']
        self.client_secret = self.params['client_secret']
        self.username = self.params['username']
        self.password = self.params['password']
        self.instance = self.params['instance']
        self.session = {'token': None}
        self.conn = None
    def login(self):