message: fix(app-shell): ensure robot update download folder exists before caching manifest
  Fixes
diff: @@ -153,13 +153,13 @@ export function getBuildrootUpdateUrls(): Promise<ReleaseSetUrls | null> {
  export function checkForBuildrootUpdate(dispatch: Dispatch): Promise<mixed> {
  const fileDownloadDir = path.join(DIRECTORY, CURRENT_VERSION)
  - return getBuildrootUpdateUrls().then(urls => {
  + return (ensureDir(fileDownloadDir): Promise<void>)
  + .then(getBuildrootUpdateUrls)
  + .then(urls => {
  if (urls === null) return Promise.resolve()
  dispatch({ type: 'buildroot:UPDATE_VERSION', payload: CURRENT_VERSION })
  - return (ensureDir(fileDownloadDir): Promise<void>)
  - .then(() => {
  let prevPercentDone = 0
  const handleProgress = progress => {
  @@ -178,7 +178,6 @@ export function checkForBuildrootUpdate(dispatch: Dispatch): Promise<mixed> {
  }
  return getReleaseFiles(urls, fileDownloadDir, handleProgress)
  - })
  .then(filepaths => cacheUpdateSet(filepaths))
  .then(updateInfo =>
  dispatch({ type: 'buildroot:UPDATE_INFO', payload: updateInfo })
  