Streaming s3 file for downloads

view.py

# using aiobotocore and plone.server(aiohttp)
ob = await client.get_object(Bucket=bucket, Key=key)

info = ob['ResponseMetadata']['HTTPHeaders']
resp = aiohttp.web.StreamResponse(headers=aiohttp.MultiDict({
    'CONTENT-DISPOSITION': 'attachment; filename="%s"' % self.filename,
    'Content-Type': info['content-type']
}))
resp.content_type = info['content-type']
resp.content_length = info['content-length']
await resp.prepare(self.request)
resp.start(self.request)
async with ob['Body'] as stream:
    file_data = await stream.read(self.chunk_size)
    while file_data:
        resp.write(file_data)
        file_data = await stream.read(self.chunk_size)
return resp