pytest: use a clean environment for all tests (#29788)

* pytest: use a clean environment for all tests

* rm that

* fix pj

* put build back

* fix params

* fix that

* handle no key

* that was removed

---------

Co-authored-by: Justin Newberry <justin@comma.ai>
old-commit-hash: 7b6afbc1623b8c159a92f6a5a951fb4d688045ee

conftest.py

@@ -0,0 +1,10 @@
+import pytest
+
+from openpilot.common.prefix import OpenpilotPrefix
+
+
+@pytest.fixture(scope="function", autouse=True)
+def global_setup_and_teardown():
+  # setup a clean environment for each test
+  with OpenpilotPrefix():
+    yield