How do I serve this video file for download using pyramid FileResponse - pyramid

Question

Please what am i missing. I keep on getting internal server error in browser when I want to serve this video file that has been downloaded on disk.
here is my code: The view function
#view_config(name='download_video')
def dl(request):
url = request.params.get('url')
camefrom = request.params.get('came_from')
path_dir = request.registry.settings['app.download_path']
result= save_to_disk(url, path_dir)
if result:
filename = result['filename']
filepath = os.path.abspath(os.path.join(path_dir,filename))
file_exists = os.path.exists(filepath)
if file_exists:
res = FileResponse(filepath,content_type='video/mp4')
res.headers['Content-Length'] = os.path.getsize(filepath)
res.headers['Content-Disposition'] = 'attachment;filename=%s'%filename
return res
request.session.flash(_("Error downloading video, please check your network","danger"))
return HTTPFound(location=camefrom)
The template
<a tal:attributes="href api.url(api.root, '##download_video', query={'came_from': request.url,'url':context.video_url})" class="btn">Download</a>
The video downloads and I can see it in the folder but I keep on getting internal server error without tracebacks on browser
My app depends on Kotti cms

Answer 1

I'm m not sure what's going on with your Pyramid logging but here is my view for downloading a file. I'm currently on an iPhone so I just cut and pasted but you should get the idea.
#view_config(route_name="download_view", renderer="")
def server_view1010(request):
filepath = os.path.join(CFG.home_dir, "static/graphics/imgs/img_sample.jpg")
if request.storage.exists(filepath): #there is no overwrite
response = FileResponse(filepath)
response.headers['Content-Disposition'] = ("attachment; filename=img_sample.jpg")
return response
else:
return Response("Unable to find: {}".format(request.path_info))