scripts/python/module/tox.ini: revise relative paths made available for source testing [#2186]

Signed-off-by: Jim Klimov <jimklimov+nut@gmail.com>

Author: jimklimov

scripts/python/module/tox.ini

@@ -15,11 +15,13 @@ envlist =
 
 [testenv]
 setenv =
-    PYTHONPATH = {toxinidir}:{toxinidir}/src/PyNUTClient
+    PYTHONPATH = {toxinidir}:{toxinidir}/PyNUTClient
 
+# On my system, some but not all Python versions complained about lack of
+# "distutils.cmd" etc. in the prepared virtual environments. Can this help?
 commands_pre =
     python -m pip install -U pip
 
 commands =
-    python src/PyNUTClient/test_nutclient.py
+    python PyNUTClient/test_nutclient.py
     #py.test --basetemp={envtmpdir}