[devtools] properly close open access on tearDown avoiding further warning about living sessions while the repo is turned off. The doc string says: The RepoAccess need to be closed to destroy the associated Session. TestCase usually take care of this aspect for the user. but that wasn't true until now.

if repo.system_source.dbdriver == 'postgres':
    sql('ALTER TABLE appears ADD COLUMN weight float')
    sql('UPDATE appears SET weight=1.0 ')