use `pathlib.Path`, remove unused aliases

setup.py

@@ -19,6 +19,7 b' requires utilities which are not available under Windows."""'
 
 import os
 import sys
+from pathlib import Path
 
 # **Python version check**
 #
@@ -61,7 +62,8 b' Python {py} detected.'
 
 # BEFORE importing distutils, remove MANIFEST. distutils doesn't properly
 # update it when the contents of directories change.
-if os.path.exists('MANIFEST'): os.remove('MANIFEST')
+if Path("MANIFEST").exists():
+    Path("MANIFEST").unlink()
 
 from distutils.core import setup
 
@@ -83,9 +85,6 b' from setupbase import ('
     unsymlink,
 )
 
-isfile = os.path.isfile
-pjoin = os.path.join
-
 #-------------------------------------------------------------------------------
 # Handle OS specific things
 #-------------------------------------------------------------------------------