Redmine_backlog installation problem in Redmine 3.2.0

[eduhernandezmon]

Hi to everyone,

I have the following Redmine environment configured on a Linux Debian 9

Environment:
  Redmine version 3.2.0.stable
  Ruby version 2.0.0-p648 (2015-12-16) [x86_64-linux]
  Rails version 4.2.5
  Environment production
  Database adapter Mysql2

I am trying to install the plugin "redmine_backlog" version 1.0.6 of the branch of this project. I follow the steps that have to be followed, resolving some conflict of gems (nokogiri, capybara and thin) and when I execute the rake redmine command: plugins: migrate RAILS_ENV = production I get the following error:

(in / var / www / redmine)
** Invoke redmine: plugins: migrate (first_time)
** Invoke environment (first_time)
** Execute environment
rake aborted!
ArgumentError: The scope body needs to be callable.
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.2.5/lib/active_record/scoping/named.rb:143:in `scope '
/var/www/redmine/plugins/redmine_backlogs/app/models/rb_release.rb:174:in `<class: RbRelease> '
/var/www/redmine/plugins/redmine_backlogs/app/models/rb_release.rb:156:in `<top (required)> '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:274:in `require '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:274:in `block in require '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:240:in `load_dependency '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:274:in `require '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:360:in `require_or_load '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:494:in `load_missing_constant '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:184:in `const_missing '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:526:in `load_missing_constant '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:184:in `const_missing '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:526:in `load_missing_constant '
/usr/local/rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:184:in `const_missing '
/var/www/redmine/plugins/redmine_backlogs/lib/backlogs_project_patch.rb:176:in `block in included '

Any clue to solve this error?

Thank you very much in advance