Yum update error

[digiteltlc (Digitel)]

yum -y update

Loaded plugins: fastestmirror, versionlock
Loading mirror speeds from cached hostfile
sng-base | 20 kB 00:00
http://sng7.com/os/7.8/os/x86_64/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-base: Damaged repomd.xml file
Trying other mirror.
sng-epel | 20 kB 00:00
http://sng7.com/sng7/epel/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-epel: Damaged repomd.xml file
Trying other mirror.
sng-extras | 20 kB 00:00
http://sng7.com/os/7.8/extras/x86_64/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-extras: Damaged repomd.xml file
Trying other mirror.
sng-pkgs | 20 kB 00:00
http://sng7.com/sng7-7.8/sng7/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-pkgs: Damaged repomd.xml file
Trying other mirror.
sng-sng7php74 | 20 kB 00:00
http://sng7.com/sng7/sng7php74/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-sng7php74: Damaged repomd.xml file
Trying other mirror.
sng-updates | 21 kB 00:00
http://sng7.com/os/7.8/updates/x86_64/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-updates: Damaged repomd.xml file
Trying other mirror.
No packages marked for update

Any suggestion ?

[dazzagrant (DarrenGrant)]

yum clean all

yum update

[digiteltlc (Digitel)]

yum clean all

Loaded plugins: fastestmirror, versionlock
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
Cleaning repos: sng-base sng-epel sng-extras sng-pkgs sng-sng7php74 sng-updates
Cleaning up list of fastest mirrors

yum -y update

Loaded plugins: fastestmirror, versionlock
Determining fastest mirrors
sng-base | 20 kB 00:00
http://sng7.com/os/7.8/os/x86_64/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-base: Damaged repomd.xml file
Trying other mirror.

One of the configured repositories failed (Sangoma-7-8.2003.5.el7.sangoma - Base),
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=sng-base ...

 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 sng-base
    or
        subscription-manager repos --disable=sng-base

 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=sng-base.skip_if_unavailable=true

failure: repodata/repomd.xml from sng-base: [Errno 256] No more mirrors to try.
http://sng7.com/os/7.8/os/x86_64/repodata/repomd.xml: [Errno -1] Error importing repomd.xml for sng-base: Damaged repomd.xml file