https://github.com/Katello/katello/commit/103eedf9581fd8b588290499af02ee0d0fcacb86

Steps to reproduce:
1. Register a system
2. Cert/key in /etc/pki/entitlement
3. curl -v --trace-ascii debug.out -d '' -k -X POST --cert /full/path/to/cert.cert --key /full/path/to/key.key https://samserver/sam/api/consumers/{consumer id}/entitlements

debug.out should show the proper header (Content-type: application/json) when there is an empty return

FAILED QA :

1. Register a system
2. Cert/key in /etc/pki/entitlement
3.# curl -v --trace-ascii debug.out -d '' -k -X POST --cert /etc/pki/entitlement/1631851920083658511.pem --key /etc/pki/entitlement/1631851920083658511-key.pem https://kvm-guest-05.rhts.eng.bos.redhat.com/sam/api/consumers/ff93b357-dddd-4a21-ab80-c55a082fa6b9/entitlements

Warning: --trace-ascii overrides an earlier trace/verbose option
{"errors":["User 8a90c5193b1bee04013b1c6258140031 is not allowed to access api/candlepin_proxies/post"],"displayMessage":"User 8a90c5193b1bee04013b1c6258140031 is not allowed to access api/candlepin_proxies/post"}
4.

That is not the correct test for this BZ. The message you show below is a failure, not an empty result. Please try again for the case where there isn't an error but instead there are no entitlements.

Verified against the same host. It works. Verified.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2013-0544.html