How to get requests with serverless lambda

I'm trying to get data from an url as a file and serve it back with the right mimetype. I've tried a lot of different options this is some of the python flask code I currently have

## download video
@app.route('/download/<string:resource>')
def download(resource):
    asset = getasset(resource)
    # headers = {"Content-Type":"application/octet-stream","Accept-Encoding":"gzip, deflate, br","Accept":"*/*"}
    response = requests.get(asset['downloads']['h264_720'], stream=True)
    # length = response.headers.get('Content-Length')

    def exhaust(response):
        while True:

            response.raw.decode_content = True 
            out = response.content.read(1024*1024)

            if not out:
                break
            yield out

    if IS_OFFLINE:
        return Response(exhaust(response), mimetype='video/mp4')      
    else:
        return Response(base64.b64decode(exhaust(response)), mimetype='video/mp4')

Offline the response is fine reviewing it locally with "serverless wsgi serve --stage dev"

Online the response is different (after doing "serverless deploy --stage dev"...

Please have a look at the image, left the correct mp4 video file. Right a file that is bigger and not a mp4 file.

It has something to do with base64.b64encode(r.content) but there is more to it. I started of with this function:

### download video
# @app.route('/download/<string:resource>')
# def download(resource):
#     asset = getasset(resource)
#     r = requests.get(asset['downloads']['h264_720'],stream=True)
    
#     if IS_OFFLINE:
#         return Response(r.content, mimetype='video/mp4')
#     else:
#         return Response(base64.b64decode(r.content), mimetype='video/mp4')

This results in a file that looks like this and is only 200 bytes:

ftypisomisomiso2avc1mp41moovlmvhdTtraktkhd8edtselst8treftmcdmdiamdhd2UhdlrvideVideoHandlerjminfvmhddinfdrefurlstblstsdavc1HH9avcCMgMPfxrhcolrnclxpaspbtrtq+Vsttsstss3estscstszOBNC7468x69G8BClAiBBKGHAEArLiDGuc=

It has some of the first characters that I can see in the correct file:

Any one knows what's going on and how to fix it?

I did manage to reproduce the issue locally:

import requests
import base64

url = 'to a video file...'

r = requests.get(url)
with open("test.mp4", "wb") as out_file:
    #reproducing the issue with this
    base64_bytes = base64.b64encode(r.content)
    #uncomment this will produce correct output
    #message_bytes = base64.b64decode(base64_bytes)
    out_file.write(message_bytes)