Redmine

Hi,

I have upgraded my redmine installation (posgresql->redmine->thin->nginx) to the new debian stable version which is now 3.0~20140825-5.
Since then I can not open the above pages in any redmine project without getting a 500 error. I have tried upgrading the database again, reconfiguring the package, accessing redmine w/o the reverse proxy and I was unable to fix the problem or to find the same bug anywhere else in the internets (nor on this site) so I open a new bug here:

production.log gives me:

Processing AdminController#index (for xxx.xxx.xxx.xxx at 2015-07-09 14:39:42) [GET]
  Parameters: {"controller"=>"admin", "action"=>"index"}

Processing ApplicationController#index (for xxx.xxx.xxx.xxx at 2015-07-09 14:39:42) [GET]
  Parameters: {"controller"=>"admin", "action"=>"index"}
/!\ FAILSAFE /!\  2015-07-09 14:39:42 +0200
  Status: 500 Internal Server Error
  cannot load such file -- action_view/template_error
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:81:in `block in log_error'
    /usr/lib/ruby/vendor_ruby/active_support/deprecation.rb:44:in `silence'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:80:in `log_error'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:142:in `rescue_action_without_handler'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:74:in `rescue_action'
    /usr/lib/ruby/vendor_ruby/action_controller/base.rb:532:in `process'
    /usr/lib/ruby/vendor_ruby/action_controller/filters.rb:606:in `process_with_filters'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:65:in `call_with_exception'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:90:in `rescue in dispatch'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:96:in `dispatch'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:121:in `_call'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:130:in `block in build_middleware_stack'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:29:in `call'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:29:in `block in call'
    /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:9:in `cache'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:28:in `call'
    /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/string_coercion.rb:25:in `call'
    /usr/lib/ruby/vendor_ruby/rack/head.rb:9:in `call'
    /usr/lib/ruby/vendor_ruby/rack/methodoverride.rb:21:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/params_parser.rb:15:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/session/cookie_store.rb:99:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/failsafe.rb:26:in `call'
    /usr/lib/ruby/vendor_ruby/rack/lock.rb:15:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:106:in `call'
    /usr/lib/ruby/vendor_ruby/rack/adapter/rails.rb:69:in `call'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:80:in `block in pre_process'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:78:in `catch'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:78:in `pre_process'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:53:in `process'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:38:in `receive_data'
    /usr/lib/ruby/vendor_ruby/eventmachine.rb:257:in `run_machine'
    /usr/lib/ruby/vendor_ruby/eventmachine.rb:257:in `run'
    /usr/lib/ruby/vendor_ruby/thin/backends/base.rb:61:in `start'
    /usr/lib/ruby/vendor_ruby/thin/server.rb:159:in `start'
    /usr/lib/ruby/vendor_ruby/thin/controllers/controller.rb:86:in `start'
    /usr/lib/ruby/vendor_ruby/thin/runner.rb:185:in `run_command'
    /usr/lib/ruby/vendor_ruby/thin/runner.rb:151:in `run!'
    /usr/bin/thin:6:in `<main>'

...when I try to open the admin page.
The error on the other pages is basicly the same:

Processing GanttsController#show (for xxx.xxx.xxx.xxx at 2015-07-09 14:40:59) [GET]
  Parameters: {"controller"=>"gantts", "action"=>"show", "project_id"=>"ox"}
Rendering template within layouts/base
Rendering gantts/show

Processing ApplicationController#show (for xxx.xxx.xxx.xxx at 2015-07-09 14:40:59) [GET]
  Parameters: {"controller"=>"gantts", "action"=>"show", "project_id"=>"ox"}
/!\ FAILSAFE /!\  2015-07-09 14:40:59 +0200
  Status: 500 Internal Server Error
  cannot load such file -- action_view/template_error
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:81:in `block in log_error'
    /usr/lib/ruby/vendor_ruby/active_support/deprecation.rb:44:in `silence'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:80:in `log_error'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:142:in `rescue_action_without_handler'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:74:in `rescue_action'
    /usr/lib/ruby/vendor_ruby/action_controller/base.rb:532:in `process'
    /usr/lib/ruby/vendor_ruby/action_controller/filters.rb:606:in `process_with_filters'
    /usr/lib/ruby/vendor_ruby/action_controller/rescue.rb:65:in `call_with_exception'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:90:in `rescue in dispatch'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:96:in `dispatch'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:121:in `_call'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:130:in `block in build_middleware_stack'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:29:in `call'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:29:in `block in call'
    /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:9:in `cache'
    /usr/lib/ruby/vendor_ruby/active_record/query_cache.rb:28:in `call'
    /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/string_coercion.rb:25:in `call'
    /usr/lib/ruby/vendor_ruby/rack/head.rb:9:in `call'
    /usr/lib/ruby/vendor_ruby/rack/methodoverride.rb:21:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/params_parser.rb:15:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/session/cookie_store.rb:99:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/failsafe.rb:26:in `call'
    /usr/lib/ruby/vendor_ruby/rack/lock.rb:15:in `call'
    /usr/lib/ruby/vendor_ruby/action_controller/dispatcher.rb:106:in `call'
    /usr/lib/ruby/vendor_ruby/rack/adapter/rails.rb:69:in `call'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:80:in `block in pre_process'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:78:in `catch'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:78:in `pre_process'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:53:in `process'
    /usr/lib/ruby/vendor_ruby/thin/connection.rb:38:in `receive_data'
    /usr/lib/ruby/vendor_ruby/eventmachine.rb:257:in `run_machine'
    /usr/lib/ruby/vendor_ruby/eventmachine.rb:257:in `run'
    /usr/lib/ruby/vendor_ruby/thin/backends/base.rb:61:in `start'
    /usr/lib/ruby/vendor_ruby/thin/server.rb:159:in `start'
    /usr/lib/ruby/vendor_ruby/thin/controllers/controller.rb:86:in `start'
    /usr/lib/ruby/vendor_ruby/thin/runner.rb:185:in `run_command'
    /usr/lib/ruby/vendor_ruby/thin/runner.rb:151:in `run!'
    /usr/bin/thin:6:in `<main>'

I'm very disappointed that an upgrade in debian "stable" now caused this unstability but what can you do right?

Postgresql version: 9.4/main
Ruby version: ruby 2.1.5p273 (2014-11-13) [x86_64-linux-gnu]
Rails version: Rails 4.1.8
...and I have no plugins installed.

Please help me, and if you require any further data, please let me know and I will post it here.