src/vs/platform/extensionManagement/node/extensionManagementService.ts/ExtensionManagementService/downloadVsix
class ExtensionManagementService:	private async downloadVsix(vsix: URI): Promise<URI> {
		if (vsix.scheme === Schemas.file) {
			return vsix;
		}
		if (!this.downloadService) {
			throw new Error('Download service is not available');
		}

		const downloadedLocation = joinPath(this.environmentService.tmpDir, generateUuid());
		await this.downloadService.download(vsix, downloadedLocation);
		return downloadedLocation;
	}