add local python path to tox testenv

Author: rekby

tox.ini

@@ -10,6 +10,7 @@ usedevelop = True
 install_command = pip install {opts} {packages}
 setenv =
     YDB_ANONYMOUS_CREDENTIALS = 1
+    PYTHONPATH = {env:PYTHONPATH}{:}{toxinidir}
 deps =
     -r{toxinidir}/test-requirements.txt