network-manager-fortisslvpn will fail with an unhelpful error if the ca file is not world readable

[Matjam]

When the "ca certificate" file is configured in the connection, but the file used is not world readable, network-manager-fortisslvpn will fail and there is no message printed.

validate_ca() in nm-fortisslvpn-service.c simply rejects the validation with no error being shown to the user, and nothing useful logged to syslog.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: network-manager-fortisslvpn-gnome 1.2.8-1build1
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: GNOME
Date: Fri May 11 10:32:05 2018
InstallationDate: Installed on 2018-05-05 (5 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: network-manager-fortisslvpn
UpgradeStatus: No upgrade log present (probably fresh install)