Error on running cron job

[bertg42]

The tasks I set up weren't appearing, so ran the job by hand from the public directory:

sudo rake --trace redmine:check_periodictasks RAILS_ENV=“production”

which returned this error (trace on):

NOTE: SourceIndex.new(hash) is deprecated; From /usr/share/redmine/config/../vendor/rails/railties/lib/rails/vendor_gem_source_index.rb:100:in new'. Please install RDoc 2.4.2+ to generate documentation. rake aborted! undefined method[]' for nil:NilClass
/usr/share/redmine/config/environment.rb:32
/usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in gem_original_require' /usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:inrequire'
/usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:182:in require' /usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:547:innew_constants_in'
/usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:182:in require' /usr/share/redmine/vendor/plugins/Redmine-Periodic-Task/lib/tasks/periodictask.rake:7 /usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:171:inload_without_new_constant_marking'
/usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:171:in load' /usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:547:innew_constants_in'
/usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:171:in load' /usr/share/redmine/vendor/rails/railties/lib/tasks/rails.rb:13 /usr/share/redmine/vendor/rails/railties/lib/tasks/rails.rb:13:ineach'
/usr/share/redmine/vendor/rails/railties/lib/tasks/rails.rb:13
/usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in gem_original_require' /usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:inrequire'
/usr/share/redmine/Rakefile:10
/usr/lib/ruby/1.8/rake.rb:2383:in load' /usr/lib/ruby/1.8/rake.rb:2383:inraw_load_rakefile'
/usr/lib/ruby/1.8/rake.rb:2017:in load_rakefile' /usr/lib/ruby/1.8/rake.rb:2068:instandard_exception_handling'
/usr/lib/ruby/1.8/rake.rb:2016:in load_rakefile' /usr/lib/ruby/1.8/rake.rb:2000:inrun'
/usr/lib/ruby/1.8/rake.rb:2068:in standard_exception_handling' /usr/lib/ruby/1.8/rake.rb:1998:inrun'
/usr/bin/rake:28

If I'm missing something obvious, let me know as I'm new to Ruby.