Fix running a Model with footprint file via AwsS3Storage

[sambles]

Fix running a Model with footprint file via AwsS3Storage

• Oasis'mf footprint bin read function checks for files and handles FileNotFoundError to detect

        try:
            lookup_file = self.storage.with_fileno(footprint_bin_lookup)
            with lookup_file as f:
                lookup = mmap.mmap(f.fileno(), length=0, access=mmap.ACCESS_READ)
            df = pickle.loads(lookup)


            self.events_dict = {
                row.event_id: (row.min_areaperil_id, row.max_areaperil_id)
                for row in df.itertuples(index=False)
            }
        except FileNotFoundError:
            self.events_dict = None

Before this fix that would cause TypeError, fixed so FileNotFoundError is raised when not found in bucket

• Added public_bucket (bool) option that sets anon = True in the S3 client settings, (anonymous user) this need an explicit setting because it prevents boto3 'walking the chain' of credentials. (for example EC2 instance with an S3 access role attached)

[vinulw]

lgtm