f = batou.component.Attribute(str) not raising exception anymore when accessing without setting

[frlan]

Having

class MyService(batou.component.Component):

    foo = batou.component.Attribute(str)

and later either

def configure(self):
    baa = self.foo

or inside Jinja

{{component.foo}}

is not raising an exeption anymore. I think this was introduced with 2.3b4 as in b3 it was still working.