bitbake: event/ast: Use better_exec instead of simple_exec

This improves the stacktraces dumped by bitbake when for example anonymous
python functions fail.

Also default to passing code strings to better_exec to match the behaviour of
simple_exec to aid the transition.

(Bitbake rev: 7e8205929ae953731a6854ea80b197847cff5771)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/event.py

@@ -175,7 +175,7 @@ def register(name, handler):
                 _handlers[name] = noop
                 return
             env = {}
-            bb.utils.simple_exec(code, env)
+            bb.utils.better_exec(code, env)
             func = bb.utils.better_eval(name, env)
             _handlers[name] = func
         else: