[CentOS] I broke "yum update" - C7

[Gary Stainburn]

Interestingly, if I try a yum update on one of my other boxes I get similar errors. However, it then proceeds to complete the yum update successfully

[root at ollie2 ~]# yum update
Loaded plugins: fastestmirror, langpacks
Determining fastest mirrors
Could not get metalink https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=x86_64 error was
14: curl#60 - "Peer's Certificate issuer is not recognized."
Could not retrieve mirrorlist https://mirror.webtatic.com/yum/el7/x86_64/mirrorlist error was
14: curl#60 - "Peer's Certificate issuer is not recognized."
 * base: mirror.as29550.net
 * epel: ftp-stud.hs-esslingen.de
 * extras: mozart.ee.ic.ac.uk
 * updates: mirror.vorboss.net
 * webtatic: uk.repo.webtatic.com
base                                                                                                                                  | 3.6 kB  00:00:00     
http://download.owncloud.org/download/repositories/10.0/CentOS_7/repodata/repomd.xml: [Errno 14] HTTPS Error 302 - Found
Trying other mirror.
extras                                                                                                                                | 3.4 kB  00:00:00     
google-chrome                                                                                                                         | 1.3 kB  00:00:00     
https://rpm.nodesource.com/pub_6.x/el/7/x86_64/repodata/repomd.xml: [Errno 14] curl#60 - "Peer's Certificate issuer is not recognized."
Trying other mirror.
It was impossible to connect to the CentOS servers.
This could mean a connectivity issue in your environment, such as the requirement to configure a proxy,
or a transparent proxy that tampers with TLS security, or an incorrect system clock.
You can try to solve this issue by using the instructions on https://wiki.centos.org/yum-errors
If above article doesn't help to resolve this issue please use https://bugs.centos.org/.

https://download.postgresql.org/pub/repos/yum/9.6/redhat/rhel-7-x86_64/repodata/repomd.xml: [Errno 14] curl#60 - "Peer's Certificate issuer is not recognized."
Trying other mirror.
updates                                                                                                                               | 3.4 kB  00:00:00     
https://uk.repo.webtatic.com/yum/el7/x86_64/repodata/repomd.xml: [Errno 14] curl#60 - "Peer's Certificate issuer is not recognized."
Trying other mirror.
https://us-east.repo.webtatic.com/yum/el7/x86_64/repodata/repomd.xml: [Errno 14] curl#60 - "Peer's Certificate issuer is not recognized."
Trying other mirror.
(1/3): google-chrome/primary                                                                                                          | 1.7 kB  00:00:00     
(2/3): extras/7/x86_64/primary_db                                                                                                     | 215 kB  00:00:00     
(3/3): updates/7/x86_64/primary_db                                                                                                    | 7.4 MB  00:00:05     
google-chrome                                                                                                                                            3/3
Resolving Dependencies