Problem runnings tests (tox and pytest)

Development
1

Sorry to ask this: I’ve made a modification to the esphome integration to add more climate support https://github.com/home-assistant/core/pull/43739.
All git tests passed, the integration works flawlessy as custom_component.
Now I’m dealing with tox to pass tests:
If I use tox I get

Failed to build homeassistant-pyozw DTLSSocket
ERROR: Could not build wheels for DTLSSocket which use PEP 517 and cannot be installed directly

If I use pytest --cov=homeassistant.components.esphome --cov-report term-missing -vv ./tests/components/esphome/
I get:

 ImportError while loading conftest '/home/fraschi/core/tests/conftest.py'.
  File "/home/fraschi/core/tests/conftest.py", line 65
    async def guard_func(*args, **kwargs):
        ^
SyntaxError: invalid syntax

Tried in venv, not-venv, docker vs, other ubuntu machine