Automated creation of release notes

Does anyone have experience in an automated creation of release notes? We already have automated nightly builds and regression tests of C++ and Python software, but we do not yet create our releases automatically.
If releases are either bug fix releases or feature releases (containing both bug fixes and enhancements), then the former would be the easiest to do: create a list of all the issues resolved between the previous release date and the current date.
For feature releases it is a little more complicated, because we do not have a well structured repository of feature requests yet.
So are there any suggested best practices that will help us create release notes automatically for in particular feature releases?