Kept like this, it yields an error on newer redmines:
Warning: the gem 'multipart-post' was found in multiple sources.
Installed from: https://rubygems.org/
Also found in:
* http://rubygems.org/
You should add a source requirement to restrict this gem to your preferred source.
For example:
gem 'multipart-post', :source => 'https://rubygems.org/'
Kept like this, it yields an error on newer redmines: