[ruby] /usr/lib/ruby/1.8/active_support/dependencies.rb:55: uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)

En una actualización de una máquina Debian con un proyecto funcionando con Ruby On Rails 1.6, hemos tenido este error al reiniciar la máquina y previa actualización:

[shell]
/var/www/vhosts/hostingaldescubierto.com/httpdocs/rails/script/server
/usr/lib/ruby/1.8/active_support/dependencies.rb:55: uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require’
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:in `require’
from /usr/lib/ruby/1.8/active_support.rb:56
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require’
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:in `require’
from /var/www/vhosts/hostingaldescubierto.com/httpdocs/rails/vendor/rails/railties/lib/commands/server.rb:1
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require’
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:in `require’
from /var/www/vhosts/hostingaldescubierto.com/httpdocs/rails/script/server:3

[/shell]

Para solucionarlo hemos usado la información que nos proporciona arunagw en stackoverflow.com

Consiste en editar el fichero boot.rb y agregar al pricipio:
[shell]
require ‘thread’
[/shell]

y en environment.rb :
[shell]
if Gem::Version.new(Gem::VERSION) >= Gem::Version.new(‘1.3.7’)
module Rails
class GemDependency
def requirement
r = super
(r == Gem::Requirement.default) ? nil : r
end
end
end
end

[/shell]

A partir de estos cambios, funciona sin problemas.