move path manipulation into single module

Change-Id: If88aafd03b757715b82cd733b3155e656c252b06
Reviewed-on: https://forge.frm2.tum.de/review/19529
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>

test/test_lib_enum.py

@@ -23,14 +23,9 @@
 
 from __future__ import division, print_function
 
-import sys
-from os import path
-
 # no fixtures needed
 import pytest
 
-sys.path.insert(0, path.abspath(path.join(path.dirname(__file__), '..')))
-
 from secop.lib.enum import Enum, EnumMember