I tried to fix a travis ci build failure.

The failure is:

  The command "wget -q --ca-certificate
$TRAVIS_BUILD_DIR/tools/lets-encrypt-x3-cross-signed.pem
https://oligarchy.co.uk/xapian/1.2.8/xapian-bindings-1.2.8.tar.gz"
failed and exited with 5 during .

Error code 5 is an SSL failure. The url given uses let's encrypt
as the CA and it looks like the travisci environment doesn't have
the cert to accept that in the ca cert file that wget uses.

I downloaded the pem cert from:

  https://letsencrypt.org/certificates/

in the intermediate cert section and this is the 

   Active
      Let’s Encrypt Authority X3 (IdenTrust cross-signed)

pem encoded cert.

I can always change the wget line to use --no-check-certificate
which is no worse than what we had before when we were using the
http url.

(note the web site changed and no longer serves via http, this failure
wasn't caused by a change to the roundup repo).