crabclient does not check proxy expiration when using --proxy

[mapellidario]

When running crab client with an expired proxy passed via --proxy option, crab client fails with the cryptic message

Singularity> crab status -d crab_recover_20230925_162750 --proxy=$X509_USER_PROXY
Fatal error trying to connect to https://cmsweb-test11.cern.ch:8443/crabserver/devtwo/info?subresource=version using subresource=version.
The server answered with an error.
Log file is /path/to/crab.log

maybe we can do better and check if the proxy is valid beforehand.

I will assign low priority because I know that this is usually not a problem, since the user is supposed to be responsible of his own proxy if he uses the --proxy option.

fyi: @novicecpp

[belforte]

ideally --proxy option is also meant to cover situation where not even voms-proxy-into is available. We could rather look into improving the message, in particular if --proxy was used.