Two db upgrade failures to detect

[gracinet]

This is for database upgrade tests. Seen on an OpenERP 7.0 project, these error swallowings:

 except ImportError:
    _logger.error('module %(addon)s: Unable to load %(stage)s-migration file %(file)s' % mergedict({'file': pyfile}, strfmt))
    raise
except AttributeError:
    _logger.error('module %(addon)s: Each %(stage)s-migration file must have a "migrate(cr, installed_version)" function' % strfmt)

trivia: in that case, the AttributeError was somewhere down the stack, i.e., not for the reason mentioned in the log