sudo yum install postgresqlはCentOS 7で動作しませんか？

CentOS 7にPostgreSQLをインストールしようとしています。このガイドDiscourseのインストール）しかし、このコマンドを実行すると：

sudo yum install postgresql91-server.x86_64 postgresql91-contrib.x86_64 postgresql91-devel.x86_64

次のエラーが発生します。

Loaded plugins: fastestmirror base                                     | 3.6 kB  00:00:00 epel/x86_64/metalink                                |  24 kB  00:00:00 extras                                              | 3.4 kB  00:00:00 nginx                                               | 2.9 kB  00:00:00 http://yum.postgresql.org/9.1/redhat/rhel-7-x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found Trying other mirror. To address this issue please refer to the below knowledge base article

https://access.redhat.com/articles/1320623

If above article doesn't help to resolve this issue please create a bug on https://bugs.centos.org/



 One of the configured repositories failed (PostgreSQL 9.1 7 - x86_64),  and yum doesn't have enough cached data to continue. At this point the only  safe thing yum can do is fail. There are a few ways to work "fix" this:

     1. Contact the upstream for the repository and get them to fix the problem.

     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).

     3. Disable the repository, so yum won't use it by default. Yum will then
        just ignore the repository until you permanently enable it again or use
        --enablerepo for temporary usage:

            yum-config-manager --disable pgdg91

     4. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=pgdg91.skip_if_unavailable=true

failure: repodata/repomd.xml from pgdg91: [Errno 256] No more mirrors to try. http://yum.postgresql.org/9.1/redhat/rhel-7-x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found

この問題を解決する方法についてのヒントはありますか？