[bind10-dev] _check_item_spec behavior

[Jeremy C. Reed]

isc.config.module_spec's _check_item_spec checks that the specification 
for a configuration data has item_optional and item_default.

Is it really necessary to fail if these don't exist? Okay if they just 
default to None?

It "Raises a ModuleSpecError if there is an error" (like missing 
item_type). This causes a python Traceback output that is many lines 
long (over a screen full) which hides the error message. I think this 
should be more friendly.

I understand that the spec files should be maintained by a BIND 10 tool, 
but possibly they could have mistakes due to personal tools or manual 
editing.

If the specification is actually corrupted, there is a "JSON parse 
error" but still many lines of Traceback output that may cause admin to 
overlook the actual problem,