rails 4: mapping values are not allowed in this context at line 2 column 11 (Psych::SyntaxError)?

Question

I have successfully installed rails 4 and created project using rails 4.0.0

rails s

for the first time was working fine. But after adding 'devise' gem in gemfile

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

and running bundle install, I am getting following error. What is the cause of this error and what will be the solution for it?

I have tried with commenting gem 'devise' section also, but now i am getting same error for every rails command.

/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'

database.yml file

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

gem 'devise' with any version, is showing following error on bundle, if I remove devise gem it works fine, I used rails 3.2.13 but I never faced such problem, what a strange.

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>'

Answer 1

If somebody still comes the same error you may to check the YAML files in your project. In this example the problem is missed indentations in database.yml. It should looks like this:

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

I get the same error but on other grounds, and the whole problem was in incorrect application.yml