The repository at 'http://opensuse-guide.org/repo/openSUSE_Leap_15.0' is
missing.  This is present for all previous Leap releases.

This repository is necessary to install the 'libdvdcss2' package.  

==> The workaround, for now, is to add the corresponding repository for Leap
42.3.



The missing repository can be added, but produces an error on refresh:

t450:~ # zypper ar -f http://opensuse-guide.org/repo/openSUSE_Leap_15.0 TEST
Adding repository 'TEST'
.....................................................................[done]
Repository 'TEST' successfully added

URI         : http://opensuse-guide.org/repo/openSUSE_Leap_15.0
Enabled     : Yes                                              
GPG Check   : Yes                                              
Autorefresh : Yes                                              
Priority    : 99 (default priority)                            

Repository priorities are without effect. All enabled repositories share the
same priority.


t450:~ # zypper ref TEST
Retrieving repository 'TEST' metadata
.......................................................[error]
Repository 'TEST' is invalid.
[TEST|http://opensuse-guide.org/repo/openSUSE_Leap_15.0] Valid metadata not
found at specified URL
Please check if the URIs defined for this repository are pointing to a valid
repository.
Skipping repository 'TEST' because of the above error.
Could not refresh the repositories because of errors.




Different return codes for Leap 15.0 versus Leap 42.3 are noted as follows:

t450:~ # wget http://opensuse-guide.org/repo/openSUSE_Leap_42.3
--2018-04-01 05:40:25--  http://opensuse-guide.org/repo/openSUSE_Leap_42.3
Resolving opensuse-guide.org (opensuse-guide.org)... 46.30.213.118
Connecting to opensuse-guide.org (opensuse-guide.org)|46.30.213.118|:80...
connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://opensuse-guide.org/repo/openSUSE_Leap_42.3/ [following]
--2018-04-01 05:40:25--  http://opensuse-guide.org/repo/openSUSE_Leap_42.3/
Reusing existing connection to opensuse-guide.org:80.
HTTP request sent, awaiting response... 403 Forbidden
2018-04-01 05:40:26 ERROR 403: Forbidden.

t450:~ # wget http://opensuse-guide.org/repo/openSUSE_Leap_15.0
--2018-04-01 05:41:01--  http://opensuse-guide.org/repo/openSUSE_Leap_15.0
Resolving opensuse-guide.org (opensuse-guide.org)... 46.30.213.118
Connecting to opensuse-guide.org (opensuse-guide.org)|46.30.213.118|:80...
connected.
HTTP request sent, awaiting response... 404 Not Found
2018-04-01 05:41:01 ERROR 404: Not Found.