```
    filename = secure_filename(mod.name) + '-' + secure_filename(version) + '.zip'
    base_path = os.path.join(secure_filename(current_user.username) + '_' + str(current_user.id), secure_filename(mod.name))
    full_path = os.path.join(_cfg('storage'), base_path)
    if not os.path.exists(full_path):
        os.makedirs(full_path)
    path = os.path.join(full_path, filename)
    for v in mod.versions:
        if v.friendly_version == secure_filename(version):
            return { 'error': True, 'reason': 'We already have this version. Did you mistype the version number?' }, 400
    if os.path.isfile(path):
        os.remove(path)        
    zipball.save(path)
    if not zipfile.is_zipfile(path):
        os.remove(path)
        return { 'error': True, 'reason': 'This is not a valid zip file.' }, 400
    version = ModVersion(secure_filename(version), game_version_id, os.path.join(base_path, filename))
    version.changelog = changelog
    # Assign a sort index
    if len(mod.versions) == 0:
        version.sort_index = 0
    else:
        version.sort_index = max([v.sort_index for v in mod.versions]) + 1
    mod.versions.append(version)
    mod.updated = datetime.now()
    if notify:
        send_update_notification(mod, version, current_user)
    db.add(version)
    db.commit()
    mod.default_version_id = version.id
    db.commit()
    notify_ckan.delay(mod_id, 'update')
    return { 'url': url_for("mods.mod", id=mod.id, mod_name=mod.name), "id": version.id  }```