This leads to multiple problems

1. We cant assume only items with id='current' are stored in the node
which would lead to retracting 'current' but another item would become
the last published and sent to users

2. Even if we have a SingletonNode retracting the only item means the Node
would be empty and offline clients would not receive the last published item
on coming online, because there is no item anymore

Instead we always publish an empty item from now on

Check for R0205 useless-object-inheritance

Check for W0611 unused-import

Check for C1801 len-as-condition

- Downgrade to glib2 2.56.2 because higher is broken on Windows 7
- Dont abort build if depchecker fails on some files

Otherwise mypy hangs because the file is to big

- Make _() available, so other modules can import it from i18n, we need
this because mypy cant handle _() in the builtins namespace

NetworkIncomingEvent defines base_network_events and generate() already

Fixes #9321