sqlalchemy.orm.exc.DetachedInstanceError: Instance <Media at 0x10949c0b8> is not bound to a Session

views.py

from pyramid.httpexceptions import HTTPNotFound, HTTPFound
from websauna.utils.slug import uuid_to_slug
from websauna.utils.slug import slug_to_uuid
from websauna.system.core import messages
from websauna.system.http import Request
from websauna.system.core.route import simple_route
from .models import Media
import pafy
import transaction

# Configure view named home at path / using a template hearit/home.html
@simple_route("/", route_name="home", renderer="hearit/home.html")
def home(request: Request):
    """Render the site homepage."""
    latest_media_list = request.dbsession.query(Media).order_by(Media.published_at.desc()).all()[:10]
    return locals()
        

@simple_route("/media/{media_uuid}", route_name="detail", renderer="hearit/detail.html")
def detail(request):

    # Convert base64 encoded UUID string from request path to Python UUID object
    media_uuid = slug_to_uuid(request.matchdict["media_uuid"])

    media = request.dbsession.query(Media).filter_by(uuid=media_uuid).one_or_none()
    if not media:
        raise HTTPNotFound()

    if request.method == "POST":
        media = request.dbsession.query(Media).filter_by(uuid=media_uuid).first()
        video = pafy.new(media.url)

        media.title = video.title
        request.dbsession.flush()
        transaction.commit()
        
        messages.add(request, msg="got the post", kind="success")
        return HTTPFound(request.route_url("fetch_media_result", media_uuid=uuid_to_slug(media.uuid)))

        if not media:
            raise HTTPNotFound()

    return locals()
    
    
@simple_route("/media/{media_uuid}/fetch_media_result", route_name="fetch_media_result", renderer="hearit/fetch_media_result.html")
def fetch_media_result(request: Request):

    # Convert base64 encoded UUID string from request path to Python UUID object
    media_uuid = slug_to_uuid(request.matchdict["media_uuid"])

    media = request.dbsession.query(Media).filter_by(uuid=media_uuid).first()
    if not media:
        raise HTTPNotFound()
    return locals()