Guzzle in drupal8 failed to connect under SLES 12
elsewhere not tested

function.php::default_ca_bundle() should add
// SLES 12
'/var/lib/ca-certificates/ca-bundle.pem',

cf. https://www.suse.com/releasenotes/x86_64/SUSE-SLES/12/
3.1.3.7 Change of Default Locations for Root Certificates REPORT BUG #