Trac #34649: remove one trace of python2

in one build script

URL: https://trac.sagemath.org/34649
Reported by: chapoton
Ticket author(s): Frédéric Chapoton
Reviewer(s): Matthias Koeppe

build/sage_bootstrap/uncompress/filter_os_files.py

@@ -1,19 +1,16 @@
 """
 Filtering out OS-specific files
 """
-
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2016 Volker Braun <[email protected]>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation, either version 2 of the License, or
 # (at your option) any later version.
-#                  http://www.gnu.org/licenses/
-#*****************************************************************************
-
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
 import os
-import sys
 
 
 def filter_os_files(filenames):
@@ -23,7 +20,6 @@ def filter_os_files(filenames):
 
     Currently removes OSX .DS_Store files and AppleDouble format ._ files.
     """
-
     files_set = set(filenames)
 
     def is_os_file(path):
@@ -45,10 +41,4 @@ def is_os_file(path):
 
         return False
 
-    filenames = filter(lambda f: not is_os_file(f), filenames)
-
-    if sys.version_info[0] == 2:
-        return filenames
-    else:
-        # Make sure to return a list on Python >= 3
-        return list(filenames)
+    return [f for f in filenames if not is_os_file(f)]