Use filter(None) for brevity

setuptools/command/easy_install.py

@@ -435,7 +435,7 @@ class easy_install(Command):
             self.pth_file = None
 
         PYTHONPATH = os.environ.get('PYTHONPATH', '').split(os.pathsep)
-        if instdir not in map(normalize_path, [_f for _f in PYTHONPATH if _f]):
+        if instdir not in map(normalize_path, filter(None, PYTHONPATH)):
             # only PYTHONPATH dirs need a site.py, so pretend it's there
             self.sitepy_installed = True
         elif self.multi_version and not os.path.exists(pth_file):