src/vs/workbench/services/userData/common/fileUserDataProvider.ts/FileUserDataProvider/readFile
class FileUserDataProvider:	readFile(resource: URI): Promise<Uint8Array> {
		if (hasReadWriteCapability(this.fileSystemProvider)) {
			return this.fileSystemProvider.readFile(this.toFileSystemResource(resource));
		}
		throw new Error('not supported');
	}