Ability to use IAM Role instead of user

[rducic]

.\main.py : Traceback (most recent call last): At line:1 char:1

• .\main.py download snap-\.\PhysicalDrive1

• 
  + CategoryInfo          : NotSpecified: (Traceback (most recent call last)::String) [], RemoteException
  + FullyQualifiedErrorId : NativeCommandError
  
  File "C:\flexible-snapshot-proxy\src\main.py", line 270, in setup_singleton
  user_account = sts.get_caller_identity().get("Account")
  File "C:\Python310\lib\site-packages\botocore\client.py", line 508, in _api_call
  return self._make_api_call(operation_name, kwargs)
  File "C:\Python310\lib\site-packages\botocore\client.py", line 898, in _make_api_call
  http, parsed_response = self._make_request(
  File "C:\Python310\lib\site-packages\botocore\client.py", line 921, in _make_request
  return self._endpoint.make_request(operation_model, request_dict)
  File "C:\Python310\lib\site-packages\botocore\endpoint.py", line 119, in make_request
  return self._send_request(request_dict, operation_model)
  File "C:\Python310\lib\site-packages\botocore\endpoint.py", line 198, in _send_request
  request = self.create_request(request_dict, operation_model)
  File "C:\Python310\lib\site-packages\botocore\endpoint.py", line 134, in create_request
  self._event_emitter.emit(
  File "C:\Python310\lib\site-packages\botocore\hooks.py", line 412, in emit
  return self._emitter.emit(aliased_event_name, **kwargs)
  File "C:\Python310\lib\site-packages\botocore\hooks.py", line 256, in emit
  return self._emit(event_name, kwargs)
  File "C:\Python310\lib\site-packages\botocore\hooks.py", line 239, in _emit
  response = handler(**kwargs)
  File "C:\Python310\lib\site-packages\botocore\signers.py", line 103, in handler
  return self.sign(operation_name, request)
  File "C:\Python310\lib\site-packages\botocore\signers.py", line 187, in sign
  auth.add_auth(request)
  File "C:\Python310\lib\site-packages\botocore\auth.py", line 407, in add_auth
  raise NoCredentialsError()
  botocore.exceptions.NoCredentialsError: Unable to locate credentials
  During handling of the above exception, another exception occurred:
  Traceback (most recent call last):
  File "C:\flexible-snapshot-proxy\src\main.py", line 457, in <module>
  setup_singleton(args)
  File "C:\flexible-snapshot-proxy\src\main.py", line 272, in setup_singleton
  except sts.exceptions as e:
  TypeError: catching classes that do not inherit from BaseException is not allowed