我已从 rails 3 切换到 ruby 2.0.0，rails 4，当我运行命令时bundle update rails出现此错误
An error occurred while installing ruby-debug-base19 (0.11.25), and Bundler cannot continue.
Make sure that `gem install ruby-debug-base19 -v '0.11.25'` succeeds before bundling.
但是当运行 gem install ruby-debug-base19 -v '0.11.25' 我得到那个错误：
Building native extensions. This could take a while...
ERROR: Error installing ruby-debug-base19:
ERROR: Failed to build gem native extension.
/home/sunloverz/.rvm/rubies/ruby-2.0.0-p247/bin/ruby extconf.rb
checking for rb_method_entry_t.body in method.h... no
checking for vm_core.h... no
/home/sunloverz/.rvm/gems/ruby-2.0.0-p247@rails-4.0/gems/ruby_core_source-0.1.5/lib/ruby_core_source.rb:39:in `create_makefile_with_core': Use RbConfig instead of obsolete and deprecated Config.
/home/sunloverz/.rvm/gems/ruby-2.0.0-p247@rails-4.0/gems/ruby_core_source-0.1.5/lib/ruby_core_source.rb:39:in `create_makefile_with_core': Use RbConfig instead of obsolete and deprecated Config.
checking for rb_method_entry_t.body in method.h... no
checking for vm_core.h... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers. Check the mkmf.log file for more details. You may
need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/home/sunloverz/.rvm/rubies/ruby-2.0.0-p247/bin/ruby
--with-ruby-dir
--without-ruby-dir
--with-ruby-include
--without-ruby-include=${ruby-dir}/include
--with-ruby-lib
--without-ruby-lib=${ruby-dir}/
/home/sunloverz/.rvm/gems/ruby-2.0.0-p247@rails-4.0/gems/ruby_core_source-0.1.5/lib/contrib/uri_ext.rb:268:in `block (2 levels) in read': Looking for http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-2.0.0-p247.tar.gz and all I got was a 404! (URI::NotFoundError)