Comment # 1 on bug 1187425 from Benjamin Zeller

This was broken by a change in the /etc/products.d/baseproduct file. When there
is no obs platform configured in the zypper.conf, zypper tries to guess the
correct one.

This is done by parsing the /etc/products.d/baseproduct file, 
in 15.2 we have:

>  <vendor>openSUSE</vendor>
>  <name>openSUSE</name>       
>  <productline>Leap</productline>

Zypper used the "name" and productline here to build the URL.
However in 15.3 we have 

>  <vendor>openSUSE</vendor>                                                                                                     
>  <name>Leap</name>                       
>  <productline>Leap</productline>

breaking the logic. Not sure if the right place to fix that is the baseproduct
file or zypp though.