On Mac OSX Yosemite, I've got following error many times with running 'bundle install'.
my process...
$ brew install rbenv
$ brew install ruby-build
$ rbenv install 2.1.2
$ rbenv rehash
$ bundle install
$ rbenv rehash
$ cd myrepos
$ bundle install
ERROR!
Gem files will remain installed in /Users/user/.gem/ruby/2.1.0/gems/debase-0.0.9 for inspection.
Results logged to /Users/user/.gem/ruby/2.1.0/extensions/x86_64-darwin-14/2.1.0-static/debase-0.0.9/gem_make.out
from /Users/user/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/ext_conf_builder.rb:38:in `block in build'
from /Users/user/.rbenv/versions/2.1.2/lib/ruby/2.1.0/tempfile.rb:324:in `open'
...
from /Users/user/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:132:in `rescue in require'
from /Users/user/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:144:in `require'
from extconf.rb:24:in `<main>'
extconf failed, exit code 1