[SOLVED] Checking the subscription behind a proxy fails.

First the patch has to be accepted, which it was.
Then you have to wait for new packages to be created that will then move through the stages:
internal staging repository -> pbstest -> pbs-no-subscription -> pbs-enterprise

So it could take a few weeks for the fix to be released.
 
It should be part of 2.2.5 and newer releases.