Redmine

I try to install redmine 2.0.4 to do a test but during the installation i have this problem :

/var/lib/gems/1.8/bin/rake generate_secret_token
(in /usr/local/share/redmine-2.0)
rake aborted!
no such file to load -- spec
/usr/local/share/redmine-2.0/Rakefile:8
(See full trace by running task with --trace)
root@empty-vmV2:/usr/local/share/redmine-2.0# /var/lib/gems/1.8/bin/rake generate_secret_token --trace
(in /usr/local/share/redmine-2.0)
rake aborted!
no such file to load -- spec
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require'
/usr/local/share/redmine-2.0/Rakefile:8
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2383:in `load'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2383:in `raw_load_rakefile'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2017:in `load_rakefile'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2016:in `load_rakefile'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2000:in `run'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/var/lib/gems/1.8/gems/rake-0.8.7/bin/rake:31
/var/lib/gems/1.8/bin/rake:19:in `load'
/var/lib/gems/1.8/bin/rake:19

If any body have an idea