Redmine

I am trying to update to redmine 1.4.2 from version 1.1.2.
I have backed up my existing redmine installation and database.
I have installed the bundler gem (version 1.1.3)

I ve executed

bundle install --without development test postgresql rmagick

which installed what was needed
but when I execute

bundle exec rake generate_session_store --trace

I get

Please install RDoc 2.4.2+ to generate documentation.
rake aborted!
builder is not part of the bundle. Add it to Gemfile.
/usr/lib/ruby/gems/1.8/gems/bundler-1.1.3/lib/bundler/rubygems_integration.rb:147:in `gem'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.14/lib/active_support/vendor.rb:4
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.14/lib/active_support.rb:55:in `require'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.14/lib/active_support.rb:55
/usr/lib/ruby/gems/1.8/gems/rails-2.3.14/lib/tasks/misc.rake:18:in `require'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.14/lib/tasks/misc.rake:18
/usr/lib/ruby/gems/1.8/gems/rails-2.3.14/lib/tasks/rails.rb:4:in `load'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.14/lib/tasks/rails.rb:4
/usr/lib/ruby/gems/1.8/gems/rails-2.3.14/lib/tasks/rails.rb:4:in `each'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.14/lib/tasks/rails.rb:4
/var/www/redmine/Rakefile:15:in `require'
/var/www/redmine/Rakefile:15
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/rake_module.rb:25:in `load'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/rake_module.rb:25:in `load_rakefile'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/application.rb:501:in `raw_load_rakefile'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/application.rb:82:in `load_rakefile'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/application.rb:81:in `load_rakefile'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/application.rb:65:in `run'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/application.rb:63:in `run'
/usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/bin/rake:33
/usr/lib/ruby/gems/1.8/bin/rake:19:in `load'
/usr/lib/ruby/gems/1.8/bin/rake:19

My gem list is

actionmailer (2.3.14)
actionpack (2.3.14)
activerecord (2.3.14)
activeresource (2.3.14)
activesupport (2.3.14)
builder (2.1.2)
bundler (1.1.3)
coderay (1.0.6)
echoe (4.3.1)
fastercsv (1.5.5)
fastthread (1.0.7)
highline (1.6.1)
hoe (2.8.0)
i18n (0.4.2)
json (1.4.6)
mysql (2.8.2)
net-ldap (0.3.1)
nokogiri (1.5.0)
racc (1.4.6)
rack (1.1.3)
rails (2.3.14)
rake (0.9.2.2, 0.8.7)
rake-compiler (0.7.5)
rdoc (3.5.1, 2.4.2)
RedCloth (4.2.9)
ruby-openid (2.1.8)
rubyforge (2.0.4)
sanitize (2.0.3)
sqlite3 (1.3.6, 1.3.3)
text-format (1.0.0)
text-hyphen (1.0.0)
tmail (1.2.7.1)
tzinfo (0.3.33, 0.3.31)

Any idea what I am doing wrong