Use pathlib in setupegg.py

This is continuation of old change: ipython#12562
which was closed due to lack of traction.
Current commit has been formatted with darker as well

setupegg.py

@@ -3,5 +3,7 @@
 
 # Import setuptools and call the actual setup
 import setuptools
-with open('setup.py', 'rb') as f:
-    exec(compile(f.read(), 'setup.py', 'exec'))
+from pathlib import Path
+
+f = Path("setup.py")
+exec(compile(f.read_text(), "setup.py", "exec"))