https://goo.gl/BGCCUC
In the near future, we will be switching to a dual release practice. There will be a “user” branch, signed with our own private key, thus locking down the system further in line with best practices and Android’s security framework. But so as not to remove the ‘hackability’ that CM is known for, we will release (in parallel) “developer” builds that will continue to be signed with the test_keys. We believe this dual release route is the best for the community, securing most users, while allowing developers an avenue to continue doing what they do best.