We had a regression when packaging Review Board extensions that was

traced to the use of static() in a class definition. This ended up

initializing some static media support before the extension packaging

code could set some state.
There's now some helpful output for this type of failure that gives the

caller some info on what may have gone wrong and how to remedy it. It

includes a reference to a new method, static_lazy().
static_lazy() works like static(), but lazily evaluates when needed,

instead of immediately. This is safe to use in class definitions, global

variables, etc., and helps prevent the kind of regression we hit.

Tested the failure case and saw the more useful error output.
Switched code to use static_lazy(), and the problem went away.