当我尝试在ruby 2.0.0-p0中安装vagrant gem时，出现以下错误：
~ ruby -v
ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux]
~ gem -v
2.0.0.rc.2
~ gem list json
*** LOCAL GEMS ***
json (1.7.7)
~ gem install vagrant
Building native extensions. This could take a while...
ERROR: Error installing vagrant:
ERROR: Failed to build gem native extension.
/home/user_name/.rvm/rubies/ruby-2.0.0-p0/bin/ruby extconf.rb
checking for ruby/re.h... yes
checking for ruby/encoding.h... yes
creating Makefile
make
compiling generator.c
generator.c: In function ‘cState_aref’:
generator.c:736:5: warning: variable ‘state’ set but not used [-Wunused-but-set-variable]
linking shared-object json/ext/generator.so
make install
/usr/bin/install -c -m 0755 generator.so /home/user_name/.rvm/gems/ruby-2.0.0-p0/gems/json-1.5.5/ext/json/ext/json/ext
/usr/bin/install: cannot create regular file `/home/user_name/.rvm/gems/ruby-2.0.0-p0/gems/json-1.5.5/ext/json/ext/json/ext': No such file or directory
make: *** [install-so] Error 1
Gem files will remain installed in /home/user_name/.rvm/gems/ruby-2.0.0-p0/gems/json-1.5.5 for inspection.
Results logged to /home/user_name/.rvm/gems/ruby-2.0.0-p0/gems/json-1.5.5/ext/json/ext/generator/gem_make.out
我想，它在构建 gem 并得到上述错误时使用来自 /home/user_name/.rvm/gems/ruby-2.0.0-p0/gems/ 的json-1.5.5 。
我尝试重新安装最新的json-1.7.7 gem，但仍然无法安装。