all: start using pathlib

Change-Id: I2b0d6ff8f534382913414fa9b35150d6f697acb4
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/34463
Reviewed-by: Alexander Zaft <a.zaft@fz-juelich.de>
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>

bin/frappy-server

@@ -24,10 +24,10 @@
 
 import argparse
 import sys
-from os import path
+from pathlib import Path
 
 # Add import path for inplace usage
-sys.path.insert(0, path.abspath(path.join(path.dirname(__file__), '..')))
+sys.path.insert(0, str(Path(__file__).absolute().parents[1]))
 
 from frappy.lib import generalConfig
 from frappy.logging import logger