[ BUG ] Passing bad credentials to a Service Class when using Credential or Object authentication produces a KeyError

[jshcodes]

Describe the bug
If you try to use Credential or Object authentication with a Service Class and provide invalid credentials when doing so, a KeyError is generated for the key 'access_token'.

To Reproduce

from falconpy import cloud_connect_aws as FalconAWS
falcon = FalconAWS.Cloud_Connect_AWS(creds={"client_id":"BadID","client_secret":"BadSecret"})
result = QueryAWSAccounts()

Results in

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/falconpy/_service_class.py", line 60, in __init__
    self.headers = {'Authorization': 'Bearer {}'.format(auth_object.token()['body']['access_token'])}
KeyError: 'access_token'

Expected behavior
The object should instantiate successfully, then generate a HTTP 401 error (access denied, invalid bearer token) when a call to the API is made.

Environment (please complete the following information):

• OS: Discovered using MacOS 10.15, assume impacts all operating systems
• Python: Discovered using Python 3.9, assume impacts all versions
• FalconPy: Affects versions 0.4.0 - 0.4.5

Additional context
Discovered while working on the multi-CID classes.