I'm trying to make this demo app work with Symfony 3. Right now it's impossible because KnpPaginatorBundle is not compatible with 3. However, I managed to make it work somehow and I'm seeing these deprecation errors:

The file "app/config/services.yml" does not contain valid YAML.

The reserved indicator "@" cannot start a plain scalar; you need to
quote the scalar at line 16 (near "arguments: [@markdown, %app_locales%]").

In services.yml we need to wrap with quotes any string that starts with @ or %. If you want to submit a pull request to solve this issue, please use single quotes instead of double quotes. Thanks!