Anon bucket still unreachable

[valeriupredoi]

Due to a unequivocal session.auth set in: reductionist.py

def get_session(username: str, password: str,
                cacert: typing.Optional[str]) -> requests.Session:
    """Create and return a client session object.

    :param username: S3 username / access key
    :param password: S3 password / secret key
    :returns: a client session object.
    """
    session = requests.Session()
    session.auth = (username, password)

Many thanks tp @sd109 for spotting this! We need a decent handling fix, and a test for it.