I am able to get rosdep working by updating ca-certificates through this
update-ca-certificates
cp /etc/ssl/certs/ca-certificates.crt /usr/lib/ssl/certs
and setting SSL_CERT_FILE variable to point to ca-certificate path
export SSL_CERT_FILE=/usr/lib/ssl/certs/ca-certificates.crt
but now rosdep dos not detect OS used by Voxl
ERROR: Rosdep experienced an error: Could not detect OS, tried ['windows', 'ubuntu', 'slackware', 'rhel', 'qnx', 'osx', 'opensuse', 'opensuse', 'mint', 'linaro', 'gentoo', 'funtoo', 'freebsd', 'fedora', 'elementary', 'debian', 'cygwin', 'centos', 'arch']