NSURLErrorDomain のコード一覧を置いておきますね。ログでコードでてきてもすぐに結びつかないので...。
| name | value |
|---|---|
| NSURLErrorUnknown | -1 |
| NSURLErrorCancelled | -999 |
| NSURLErrorBadURL | -1000 |
| NSURLErrorTimedOut | -1001 |
| NSURLErrorUnsupportedURL | -1002 |
| NSURLErrorCannotFindHost | -1003 |
| NSURLErrorCannotConnectToHost | -1004 |
| NSURLErrorNetworkConnectionLost | -1005 |
| NSURLErrorDNSLookupFailed | -1006 |
| NSURLErrorHTTPTooManyRedirects | -1007 |
| NSURLErrorResourceUnavailable | -1008 |
| NSURLErrorNotConnectedToInternet | -1009 |
| NSURLErrorRedirectToNonExistentLocation | -1010 |
| NSURLErrorBadServerResponse | -1011 |
| NSURLErrorUserCancelledAuthentication | -1012 |
| NSURLErrorUserAuthenticationRequired | -1013 |
| NSURLErrorZeroByteResource | -1014 |
| NSURLErrorCannotDecodeRawData | -1015 |
| NSURLErrorCannotDecodeContentData | -1016 |
| NSURLErrorCannotParseResponse | -1017 |
| NSURLErrorAppTransportSecurityRequiresSecureConnection | -1022 |
| NSURLErrorFileDoesNotExist | -1100 |
| NSURLErrorFileIsDirectory | -1101 |
| NSURLErrorNoPermissionsToReadFile | -1102 |
| NSURLErrorDataLengthExceedsMaximum | -1103 |
| NSURLErrorFileOutsideSafeArea | -1104 |
| NSURLErrorSecureConnectionFailed | -1200 |
| NSURLErrorServerCertificateHasBadDate | -1201 |
| NSURLErrorServerCertificateUntrusted | -1202 |
| NSURLErrorServerCertificateHasUnknownRoot | -1203 |
| NSURLErrorServerCertificateNotYetValid | -1204 |
| NSURLErrorClientCertificateRejected | -1205 |
| NSURLErrorClientCertificateRequired | -1206 |
| NSURLErrorCannotLoadFromNetwork | -2000 |
| NSURLErrorCannotCreateFile | -3000 |
| NSURLErrorCannotOpenFile | -3001 |
| NSURLErrorCannotCloseFile | -3002 |
| NSURLErrorCannotWriteToFile | -3003 |
| NSURLErrorCannotRemoveFile | -3004 |
| NSURLErrorCannotMoveFile | -3005 |
| NSURLErrorDownloadDecodingFailedMidStream | -3006 |
| NSURLErrorDownloadDecodingFailedToComplete | -3007 |
| NSURLErrorInternationalRoamingOff | -1018 |
| NSURLErrorCallIsActive | -1019 |
| NSURLErrorDataNotAllowed | -1020 |
| NSURLErrorRequestBodyStreamExhausted | -1021 |
| NSURLErrorBackgroundSessionRequiresSharedContainer | -995 |
| NSURLErrorBackgroundSessionInUseByAnotherProcess | -996 |
| NSURLErrorBackgroundSessionWasDisconnected | -997 |
出典) https://github.com/apple/swift-corelibs-foundation/blob/master/Sources/Foundation/NSURLError.swift