Redmine (1.4.7) error in executing server in development mode

While running redmine 1.4.7 in development mode using the command rails s, I have got error like below

 /usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/options.rb:32:in
 `default_options': undefined method `write_inheritable_attribute' for
 Rails::Generator::Base:Class (NoMethodError)
         from /usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/base.rb:90:in
 `<class:Base>'
         from /usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/base.rb:85:in
 `<module:Generator>'
         from /usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/base.rb:48:in
 `<module:Rails>'
         from /usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/base.rb:6:in
 `<top (required)>'
         from /usr/local/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:126:in
 `require'
         from /usr/local/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:126:in
 `require'
         from /usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator.rb:37:in
 `<top (required)>'
         from /usr/local/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:126:in
 `require'
         from /usr/local/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:126:in
 `require'
         from /usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/bin/rails:15:in    `<top
 (required)>'
         from /usr/local/bin/rails:23:in `load'
         from /usr/local/bin/rails:23:in `<main>'

I have spent about 2 hours for fixing it and got some references from this link
and now am getting this error. How can I fix this??

/usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/generators/applications/app/app_generator.rb:7:in `<class:AppGenerator>': Use RbConfig instead of obsolete and deprecated Config.
/usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/generators/applications/app/app_generator.rb:7:in `<class:AppGenerator>': Use RbConfig instead of obsolete and deprecated Config.
/usr/local/lib/ruby/gems/2.0.0/gems/rails-2.3.15/lib/rails_generator/generators/applications/app/app_generator.rb:7:in `<class:AppGenerator>': Use RbConfig instead of obsolete and deprecated Config.
undefined method `camelize' for "app":String

Upvotes: 1