CRAN check fails when LLNL ESGF node is not available

[hongyuanjia]

Comments from Brian Ripley:

There is a variety of failures here, it seems both in contacting a
website and in the content of that site.  We need to remind you of the
CRAN policy

'Packages which use Internet resources should fail gracefully with an
informative message if the resource is not available or has changed (and
not give a check warning nor error).'

so this needs correction whether or not the resource recovers.