Problem runnings tests (tox and pytest)

Sorry to ask this: I’ve made a modification to the esphome integration to add more climate support
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/'.
  File "/home/fraschi/core/tests/", line 65
    async def guard_func(*args, **kwargs):
SyntaxError: invalid syntax

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