我不小心删除了postgressSQL，现在我无法使用yum命令。每次我尝试使用它，我都会遇到一个问题。有人能帮我解决这个问题吗？

[root@centos ~]# sudo yum check-update
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
epel/x86_64/metalink                                                                                      | 7.8 kB  00:00:00
 * base: mirrors.nxtgen.com
 * epel: repo.extreme-ix.org
 * extras: mirrors.nxtgen.com
 * updates: mirrors.nxtgen.com
Artifactory/signature                                                                                     |  183 B  00:00:00
Artifactory/signature                                                                                     | 1.5 kB  00:00:00 !!!
Artifactory-pro/signature                                                                                 |  183 B  00:00:00
Artifactory-pro/signature                                                                                 | 1.5 kB  00:00:00 !!!
base                                                                                                      | 3.6 kB  00:00:00
docker-ce-stable                                                                                          | 3.5 kB  00:00:00
extras                                                                                                    | 2.9 kB  00:00:00
hashicorp                                                                                                 | 1.4 kB  00:00:00
jenkins                                                                                                   | 2.9 kB  00:00:00
pgdg-common/7/x86_64/signature                                                                            |  665 B  00:00:00
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-PGDG
pgdg-common/7/x86_64/signature                                                                            | 2.9 kB  00:00:00 !!!
https://download.postgresql.org/pub/repos/yum/common/redhat/rhel-7-x86_64/repodata/repomd.xml: [Errno -1] Gpg Keys not imported, cannot verify repomd.xml for repo pgdg-common
Trying other mirror.

 One of the configured repositories failed (PostgreSQL common RPMs for RHEL / CentOS 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. Run the command with the repository temporarily disabled
            yum --disablerepo=pgdg-common ...

     4. Disable the repository permanently, 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 pgdg-common
        or
            subscription-manager repos --disable=pgdg-common

     5. 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=pgdg-common.skip_if_unavailable=true

failure: repodata/repomd.xml from pgdg-common: [Errno 256] No more mirrors to try.
https://download.postgresql.org/pub/repos/yum/common/redhat/rhel-7-x86_64/repodata/repomd.xml: [Errno -1] Gpg Keys not imported, cannot verify repomd.xml for repo pgdg-common
[root@centos ~]#

字符串