Receiving the error in a local variable only to assert there is none
is less clear than passing &error_abort.  Clean up.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20200630090351.1247703-5-armbru@redhat.com>