Raise non 404 Error in generate-tempest-plugin-list.py
Raise non 404 Error in generate-tempest-plugin-list.py

This commit makes the tempest plugin function raise non 404 errors
when it catches them. Without doing that, we just ignore the errors.
However we shouldn't do that because it just causes another error when
the variable is used.

Change-Id: Ia82ef2aa9cb0959ccee1600feff297abb451176a

openstack/tempest,masayukig/tempest,masayukig/tempest,openstack/tempest,cisco-openstack/tempest,cisco-openstack/tempest