Port auth remotebackend tests to Python

[fredmorcos]

• Program: Authoritative
• Issue type: Bug report

Short description

The remotebackend tests work by running a Ruby webserver then some clients connect to it and exchange data. We should port these Ruby webservers to Python.

• There is some shell scripting that I would also like to see moved over to Python.
• The Python webserver should be a module which we can import and use from other Python code e.g. to easily integrate it with our CI scripts and properly handle errors and exceptions instead of relying on executable shell scripts and return codes.
• The resulting Python code should be idiomatic, well formatted and delinted, and using venvs.

See the unittest*.rb files over here: https://github.com/PowerDNS/pdns/tree/master/modules/remotebackend

A good starting point is https://github.com/cmouse/pdns-remotebackend-python. It is currently incomplete as it only handles the pipe and unix connectors.