Report when server severs connection

If an exception occurs while trying to connect to the server (e.g. if the
server has an exception which severs the connection, an unrelated and
unhandled exception is being thrown. This fixes that.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-332
probably best as just `#{e}` which is implicitly `e.to_s`, rather than trying to filter only parts of the data out.