function readBlob(resp, info):Promise<Blob> {
  log.verbose('readBlob', resp, info)
  return resp.blob()
}
Get response data as RNFetchBlob Blob polyfill object.
@param  {FetchBlobResponse} resp Response data object from RNFB fetch call.
@param  {RNFetchBlobResponseInfo} info Response informations.
@return {Promise<Blob>}