Fixed #10 — S3Bucket.listdir() method raise UnboundLocalError sometimes

[dahlia]

S3Bucket.listdir() method raised UnboundLocalError when the result list is empty. This patch fixes the bug. You can reproduce the bug by running following code:

from simples3.bucket import S3Bucket

S3_BUCKET_NAME = '...'
S3_ACCESS_KEY = '...'
S3_SECRET_KEY = '...'

bucket = S3Bucket(S3_BUCKET_NAME, S3_ACCESS_KEY, S3_SECRET_KEY)

# The above code works well both.
for x in bucket.listdir(prefix='existing-prefix'):
    print x

# The above code works only after this patch.
for x in bucket.listdir(prefix='not-existing-prefix'):
    print x

This bug fix has done by Hyunjun Kim, an employee of my company. Thank you!

[lericson]

Fixed in 56cb4aac30bfca9c1f8872656c80910d19551e73