docs: def install_napp(cls, mgr):
          """Install a NApp.
  
          Raises:
              KytosException: If a NApp hasn't been found.
  
          """
          try:
              LOG.info('    Searching local NApp...')
              mgr.install_local()
              LOG.info('    Found and installed.')
          except FileNotFoundError:
              LOG.info('    Not found. Downloading from NApps Server...')
              try:
                  mgr.install_remote()
                  LOG.info('    Downloaded and installed.')
                  return
              except HTTPError as exception:
                  if exception.code == 404:
                      LOG.error('    NApp not found.')
                  else:
                      LOG.error('    NApps Server error: %s', exception)
              except URLError as exception:
                  LOG.error('    NApps Server error: %s', str(exception.reason))
              raise KytosException("NApp not found.")