Comment # 1 on bug 1048842 from Max Lin

seems it is a infrastructure problem therefore the installer failed to download
the release note from
https://doc.opensuse.org/release-notes/x86_64/openSUSE/Leap/42.3/RELEASE-NOTES.en.rtf

per curl_log:

* Hostname was NOT found in DNS cache
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0*
  Trying 195.135.221.140...
* connect to 195.135.221.140 port 80 failed: Connection refused
*   Trying 2001:67c:2178:8::16...
* connect to 2001:67c:2178:8::16 port 80 failed: Network is unreachable
* Failed to connect to doc.opensuse.org port 80: Network is unreachable
* Closing connection 0
curl: (7) Failed to connect to doc.opensuse.org port 80: Network is unreachable