When developing specs its useful to know which attr space
YNL was trying to find an attribute in on key error.

Instead of printing:
 KeyError: 0
add info about the space:
 Exception: Space 'vport' has no attribute with value '0'
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20230814205627.2914583-4-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>