test: add conftest to ensure src is importable in CI

Author: andrepsousa

tests/conftest.py

@@ -1,6 +1,6 @@
 import os
 import sys
 
-PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(_file_), ".."))
+PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), ".."))
 if PROJECT_ROOT not in sys.path:
     sys.path.insert(0, PROJECT_ROOT)