{'expiration': '2007-12-01T12:00:00.000Z', 'conditions': [{'bucket':
    'johnsmith'}, ['starts-with', '$key', 'user/eric/'], {'acl':
    'public-read'}, {'redirect':
    'http://johnsmith.s3.amazonaws.com/successful_upload.html'}, [
    'starts-with', '$Content-Type', 'image/'], {'x-amz-meta-uuid':
    '14365123651274'}, ['starts-with', '$x-amz-meta-tag', '']]}
Python Generated Signature for S3 Post