Comment 3 for bug 956562

I got this problem when I need s3token authentication from swift. Please check your keystone configuration that has [filter:s3_extension] section in your keystone configuration. If it disappear on keystone.conf that is a problem because the default keystone.conf didn't add this section. I add configuration below:

[filter:s3_extension]
paste.filter_factory = keystone.contrib.s3:S3Extension.factory

# and modify api

[pipeline:public_api]
pipeline = token_auth admin_token_auth xml_body json_body debug ec2_extension s3_extension public_service

[pipeline:admin_api]
pipeline = token_auth admin_token_auth xml_body json_body debug ec2_extension s3_extension crud_extension admin_service

Then restart keystone and try it again.
If you have same problem like me, maybe this solution can help you.