Redmine

You can see Travis builds failing because of rake 11 here https://travis-ci.org/ixti/redmine_tags/jobs/115069169.

The solution I found here: http://stackoverflow.com/questions/35893584/nomethoderror-undefined-method-last-comment-after-upgrading-to-rake-11 fixes the problem.

Basically you have to add the following inside the Gemfile:

gem 'rake', '< 11.0'

The other solution (patching rake) is kind of ugly but may work better long term.
Not sure which one to choose for a patch.

To make my builds pass I added the following in .travis.yml before_install hook:

echo "gem 'rake', '< 11.0'" >> Gemfile