Some distributions, notably Ubuntu 16.04 and OpenSUSE Tumbleweed (as of
22.10.17) ship an older version of uncrustify. This version may report
formatting errors.
Travis host images are quite outdated, so the builds will now use containers
instead. By default there's a build for Arch Linux (using base/archlinux:latest
image) and Fedora (using official fedora:latest).
Builds are done using extra/travis-build script.