Same error over here. Skyscraper 2.9.5. With igdb API-Key.
Adding --verbosity 3 adds no extra details.
Just to make sure your API-key is right, try:
curl 'https://api-endpoint.igdb.com/games' -H 'user-key: <your_key_here>' --> should return an authentication failure AND
curl 'https://api-v3.igdb.com/games' -H 'user-key: <your_key_here>' --> should give you a JSON formatted array of ten records.
So the URL changed from api-endpoint.igdb.com to api-v3.igdb.com.
By the time I will file a PR at Github. In the meantime you can help yourself:
sudo ~/RetroPie-Setup/retropie_packages.sh skyscraper depends
sudo ~/RetroPie-Setup/retropie_packages.sh skyscraper sources
Do edits in ~/RetroPie-Setup/tmp/build/skyscraper/src/igdb.cpp: The values of the variables baseUrl and searchUrlPre should reflect the new URL.
Then:
sudo ~/RetroPie-Setup/retropie_packages.sh skyscraper get_opts
sudo ~/RetroPie-Setup/retropie_packages.sh skyscraper get_bins
sudo ~/RetroPie-Setup/retropie_packages.sh skyscraper build
sudo ~/RetroPie-Setup/retropie_packages.sh skyscraper install
Clean (optional):
sudo ~/RetroPie-Setup/retropie_packages.sh skyscraper clean
Run Skyscraper again as in your original post. It should work then.
HTH