Feature request : requesting VO services with mirrors

It could be great if the user could give a list of mirrors for requesting a specific VO service like this :

>>> scs_srv = vo.dal.SCSService([
>>> 'mirror_1',
>>> ...,
>>> 'mirror_n'])
>>> scs_results = scs_srv.search(pos=pos, radius=size)

Something like, if the first mirror does not respond (DALServiceError raised) one can ask the second etc...

Start by locating the SCSService entry point and the DALServiceError handling in the Python package, then trace how a service request is sent. The feature is done when SCSService accepts multiple mirror URLs and tries the next mirror after an unresponsive service raises DALServiceError; add or update tests for this fallback behavior.

Written by the indexing model from the issue text.