src/vs/platform/update/electron-main/updateService.linux.ts/LinuxUpdateService/doCheckForUpdates
class LinuxUpdateService:	protected doCheckForUpdates(context: any): void {
		if (!this.url) {
			return;
		}

		this.setState(State.CheckingForUpdates(context));
		this.requestService.request({ url: this.url }, CancellationToken.None)
			.then<IUpdate | null>(asJson)
			.then(update => {
				if (!update || !update.url || !update.version || !update.productVersion) {
					this.telemetryService.publicLog2<{ explicit: boolean }, UpdateNotAvailableClassification>('update:notAvailable', { explicit: !!context });

					this.setState(State.Idle(UpdateType.Archive));
				} else {
					this.setState(State.AvailableForDownload(update));
				}
			})
			.then(undefined, err => {
				this.logService.error(err);
				this.telemetryService.publicLog2<{ explicit: boolean }, UpdateNotAvailableClassification>('update:notAvailable', { explicit: !!context });
				// only show message when explicitly checking for updates
				const message: string | undefined = !!context ? (err.message || err) : undefined;
				this.setState(State.Idle(UpdateType.Archive, message));
			});
	}