centosにlibyaml-develをいれようとしたときにerrorがでる場合の対処法

#概要
カスタマイズされたruby環境を整えるためのcookbookを作っていたんだけど、毎回yum install libyaml-devel で謎のエラーがでて、対処法を思い出すのに時間がかかるため、メモっておく

#エラー内容

---> Package glibc-headers.x86_64 0:2.12-1.149.el6_6.5 will be an update
---> Package nss-softokn-freebl.x86_64 0:3.14.3-9.el6 will be updated
---> Package nss-softokn-freebl.i686 0:3.14.3-22.el6_6 will be installed
---> Package nss-softokn-freebl.x86_64 0:3.14.3-22.el6_6 will be an update
--> Finished Dependency Resolution
Error:  Multilib version problems found. This often means that the root
       cause is something else and multilib version checking is just
       pointing out that there is a problem. Eg.:

         1. You have an upgrade for libyaml which is missing some
            dependency that another package requires. Yum is trying to
            solve this by installing an older version of libyaml of the
            different architecture. If you exclude the bad architecture
            yum will tell you what the root cause is (which package
            requires what). You can try redoing the upgrade with
            --exclude libyaml.otherarch ... this should give you an error
            message showing the root cause of the problem.

         2. You have multiple architectures of libyaml installed, but
            yum can only see an upgrade for one of those arcitectures.
            If you don't want/need both architectures anymore then you
            can remove the one with the missing update and everything
            will work.

         3. You have duplicate versions of libyaml installed already.
            You can use "yum check" to get yum show these errors.

       ...you can also use --setopt=protected_multilib=false to remove
       this checking, however this is almost never the correct thing to
       do as something else is very likely to go wrong (often causing
       much more problems).

       Protected multilib versions: libyaml-0.1.3-4.el6_6.i686 != libyaml-0.1.6-1.el6.x86_64
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

こんな感じのエラーが出る。ちょっとググった感じだと、だいたいepelを設定しろみたいな感じの対処法がでてくるが、そういう話じゃないっぽい。むしろ、それがノイズになって、毎回対処法が出てこなくなる。

#対処法
ここに載っていた
libyaml architecture check during install · Issue #3206 · wayneeseguin/rvm

# yum downgrade libyaml
# yum install libyaml-devel

これで行けた。