Which adds --non-interactive and --trust-server-cert to the svn
checkout and update command lines. This allows ExternalProject
clients to pull from an https:// based svn server even though
the server may not have a valid or trusted certificate.

Caveat emptor: I would NOT recommend using this except as a
short-term work-around. Rather, the server should have a valid,
trusted certificate, or the client should be using "http" instead
of "https".