Description of problem:
When I want to use new GCC for testing on an aarch64 platform, I follow the steps in the wiki page https://www.softwarecollections.org/en/scls/rhscl/devtoolset-7/
But it will report an error because the URL is invalid http://mirror.centos.org/centos/7/sclo/aarch64/rh/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found.
No such repository in the sclo folder. Its location starts with "buildlogs"

Version-Release number of selected component (if applicable):
CentOS Linux release 7.4.1708 (AltArch)
Linux server01.local 4.11.0-45.4.1.el7a.aarch64 #1 SMP Fri Feb 2 17:11:57 UTC 2018 aarch64 aarch64 aarch64 GNU/Linux

How reproducible:
Just type the command as the described on the page "https://www.softwarecollections.org/en/scls/rhscl/devtoolset-7/"

Steps to Reproduce:
1. sudo yum install centos-release-scl-rh
2. sudo yum-config-manager --enable centos-sclo-rh-testing
3. sudo yum install devtoolset-7

Actual results:
Loaded plugins: fastestmirror, langpacks
http://mirror.centos.org/centos/7/sclo/aarch64/rh/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
To address this issue please refer to the below wiki article 

https://wiki.centos.org/yum-errors

If above article doesn't help to resolve this issue please use https://bugs.centos.org/.



 One of the configured repositories failed (CentOS-7 - SCLo rh),
 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=centos-sclo-rh ...

     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 centos-sclo-rh
        or
            subscription-manager repos --disable=centos-sclo-rh

     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=centos-sclo-rh.skip_if_unavailable=true

failure: repodata/repomd.xml from centos-sclo-rh: [Errno 256] No more mirrors to try.
http://mirror.centos.org/centos/7/sclo/aarch64/rh/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found


Expected results:
Succeed to install the devtoolsets

Additional info:
yum --disablerepo="centos-sclo-rh" install scl-utils-build scl-utils
yum --disablerepo="*" --enablerepo="centos-sclo-rh-testing" install devtoolset-7-gcc*

These commands - with disable/enable repository - could work properly