Add better handling for other Discogs errors

[jch254]

E.g. 502 response:

{
    "errorMessage": "Status code 502",
    "errorType": "Error",
    "stackTrace": [
        "Error: Status code 502",
        "    at ClientRequest.<anonymous> (/Users/jch254/Dev/jch254/proj/discogs-market-monitor/node_modules/rss-parser/lib/parser.js:88:25)",
        "    at Object.onceWrapper (node:events:640:26)",
        "    at ClientRequest.emit (node:events:520:28)",
        "    at ClientRequest.emit (node:domain:475:12)",
        "    at HTTPParser.parserOnIncomingClient (node:_http_client:618:27)",
        "    at HTTPParser.parserOnHeadersComplete (node:_http_common:128:17)",
        "    at TLSSocket.socketOnData (node:_http_client:482:22)",
        "    at TLSSocket.emit (node:events:520:28)",
        "    at TLSSocket.emit (node:domain:475:12)",
        "    at addChunk (node:internal/streams/readable:315:12)",
        "    at readableAddChunk (node:internal/streams/readable:289:9)",
        "    at TLSSocket.Readable.push (node:internal/streams/readable:228:10)",
        "    at TLSWrap.onStreamRead (node:internal/stream_base_commons:190:23)"
    ]
}