travis-ci: install cmake from xenial (CTEST_PARALLEL_LEVEL support) cmake supports it since 3.0 I guess. And it must be trusty (not precise), otherwise it fails: dpkg: error processing /var/cache/apt/archives/ifupdown_0.8.10ubuntu1_amd64.deb (--unpack): trying to overwrite '/etc/init.d/networking', which is also in package netbase 4.47ubuntu1 Link: https://travis-ci.org/azat/libevent/jobs/193744023