Hi,
today PR #4709 was merged to Foreman core, which sets Rails 5.0.6 as
default when using Ruby >= 2.3.
All plugin authors should now start to make their plugins compatible
with Rails 5.0, as Foreman 1.17 will very likely not support Rails 4.2
anymore.
RPM and DEB builds are not affected at this moment, as RPMs still use
Ruby 2.2 and DEBs are pinned to Rails 4.2 for compatibility reasons
with currently released plugin versions.
Regards