pkgs/den-http-get-updater: try evaluate urlLocation multiple times

pkgs/by-name/de/den-http-get-updater/package.nix

@@ -113,10 +113,21 @@ writeScript "den-http-get-updater" (''
   nixUnpack = lib.optionalString unpack "--unpack";
   nixName = lib.optionalString (!builtins.isNull name) "--name \"${lib.escapeShellArg name}\"";
 in ''
-  nixUrlsResult=$(nix-instantiate --eval --json --strict \
-    "${prefetchUrlLocationShellEscape.file}" \
-    -A "${prefetchUrlLocationShellEscape.attrpath}"
-  )
+  for i in {{ 1..30 }}; do
+    nixUrlsResult=$(nix-instantiate --eval --json --strict \
+        "${prefetchUrlLocationShellEscape.file}" \
+        -A "${prefetchUrlLocationShellEscape.attrpath}"
+      )
+      if [[ "$?" == "0" ]]; then
+          break
+      elif [[ "$i" == 30 ]]; then
+          echo "error: prefetchUrlLocation failed - attempts exhausted" 1>&2
+          exit 1
+      fi
+      echo "prefetchUrlLocation failed (attempt $i)" 1>&2
+      sleep 2
+  done
+
 
   urlsType=$(jq -rc 'type' <<< "$nixUrlsResult")
   if [ "$urlsType" = "array" ]; then