S3 hook causing exception from credentials unpacking

[vaughnkoch]

I'm seeing this exception using Airflow v1.10.0rc2.

Traceback (most recent call last):
  File "******/data/virtualenvs/airpipe/bin/airflow", line 32, in <module>
    args.func(args)
  File "******/data/virtualenvs/airpipe/lib/python3.6/site-packages/airflow/utils/cli.py", line 74, in wrapper
    return f(*args, **kwargs)
  File "******/data/virtualenvs/airpipe/lib/python3.6/site-packages/airflow/bin/cli.py", line 593, in test
    ti.run(ignore_task_deps=True, ignore_ti_state=True, test_mode=True)
  File "******/data/virtualenvs/airpipe/lib/python3.6/site-packages/airflow/utils/db.py", line 74, in wrapper
    return func(*args, **kwargs)
  File "******/data/virtualenvs/airpipe/lib/python3.6/site-packages/airflow/models.py", line 1723, in run
    session=session)
  File "******/data/virtualenvs/airpipe/lib/python3.6/site-packages/airflow/utils/db.py", line 70, in wrapper
    return func(*args, **kwargs)
  File "******/data/virtualenvs/airpipe/lib/python3.6/site-packages/airflow/models.py", line 1632, in _run_raw_task
    result = task_copy.execute(context=context)
  File "******/airflow/plugins/snowflake_plugin/operators/s3_to_snowflake_operator.py", line 75, in execute
    sql = self.build_copy()
  File "******/airflow/plugins/snowflake_plugin/operators/s3_to_snowflake_operator.py", line 44, in build_copy
    s3_hook = S3Hook(self.s3_conn_id)
ValueError: too many values to unpack (expected 2)

This seems to be caused by the fact that get_credentials is returning a ReadOnlyCredentials object which isn't a 2-tuple, but the code expects a 2-tuple.

ipdb> s3_hook.get_credentials()
ReadOnlyCredentials(access_key='*************', secret_key='*************', token=None)

Code failing:

a_key , s_key = s3_hook.get_credentials()