Eu instalei o rails 4 e criei o projeto usando rails 4.0.0

rails s

pela primeira vez estava funcionando bem. Mas depois de adicionar gem 'legado' no gemfile

 gem 'devise', '~> 3.0.0.rc'

e executando a instalação do pacote, estou recebendo o seguinte erro. Qual é a causa desse erro e qual será a solução para isso?

Eu tentei com comentando gem 'conceber' seção também, mas agora eu estou recebendo o mesmo erro para cada comando trilhos.

/home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:205:in `parse':   (<unknown>): mapping values are not allowed in this context at line 2 column 11 (Psych::SyntaxError)
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:205:in `parse_stream'
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:153:in `parse'
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:129:in `load'
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/rubygems/config_file.rb:318:in `load_file'
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/rubygems/config_file.rb:191:in `initialize'
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/rubygems/gem_runner.rb:66:in `new'
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/rubygems/gem_runner.rb:66:in `do_configuration'
from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/rubygems/gem_runner.rb:46:in `run'

arquivo database.yml

development:
adapter: mysql2
encoding: utf8
database: realstate_development
pool: 5
username: root
password: root
socket: /var/run/mysqld/mysqld.sock

gem 'conceber' com qualquer versão, está mostrando o seguinte erro no pacote, se eu remover gem conceber ele funciona bem, eu usei rails 3.2.13, mas eu nunca enfrentei esse problema, que estranho.

Fetching gem metadata from https://rubygems.org/.........
Fetching gem metadata from https://rubygems.org/..
Unfortunately, a fatal error has occurred. Please see the Bundler troubleshooting documentation at http://bit.ly/bundler-issues. Thanks!
/home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:205:in `parse': (<unknown>): mapping values are not allowed in this context at line 2 column 11 (Psych::SyntaxError)
    from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:205:in `parse_stream'
    from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:153:in `parse'
    from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/psych.rb:129:in `load'
    from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/rubygems/config_file.rb:318:in `load_file'
    from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/rubygems/config_file.rb:191:in `initialize'
    from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/rubygems.rb:319:in `new'
    from /home/siv/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/rubygems.rb:319:in `configuration'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/rubygems_integration.rb:34:in `configuration'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/rubygems_integration.rb:53:in `sources='
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/source/rubygems.rb:250:in `remote_specs'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/source/rubygems.rb:163:in `fetch_specs'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/source/rubygems.rb:67:in `specs'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/definition.rb:192:in `block (2 levels) in index'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/definition.rb:189:in `each'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/definition.rb:189:in `block in index'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/index.rb:9:in `build'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/definition.rb:185:in `index'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/definition.rb:179:in `resolve'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/definition.rb:114:in `specs'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/definition.rb:109:in `resolve_remotely!'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/installer.rb:83:in `run'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/installer.rb:14:in `install'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/cli.rb:247:in `install'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/vendor/thor/task.rb:27:in `run'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/vendor/thor/invocation.rb:120:in `invoke_task'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/vendor/thor.rb:344:in `dispatch'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/vendor/thor/base.rb:434:in `start'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/bin/bundle:20:in `block in <top (required)>'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/friendly_errors.rb:3:in `with_friendly_errors'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/bin/bundle:20:in `<top (required)>'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/bin/bundle:23:in `load'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247@global/bin/bundle:23:in `<main>'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247/bin/ruby_noexec_wrapper:14:in `eval'
    from /home/siv/.rvm/gems/ruby-2.0.0-p247/bin/ruby_noexec_wrapper:14:in `<main>'