bitbake: bb.fatal: Raise a BBHandledException instead of exiting

With new bitbake UIs having the cooker exit at 'random' points
in the codebase is problematic. This patch raises an exception
which matches the siutation instead.

(Bitbake rev: a50017ba71250e1710a6425b60ac7e3f03d88295)

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

bitbake/lib/bb/__init__.py

@@ -99,8 +99,7 @@ def error(*args):
 
 def fatal(*args):
     logger.critical(''.join(args))
-    sys.exit(1)
-
+    raise BBHandledException()
 
 def deprecated(func, name=None, advice=""):
     """This is a decorator which can be used to mark functions