sort.py: print errors to stderr

Misc: The trailing comma is due to using the opinionated `black` Python
formatter (which seems to be a relatively common one).  This was the
only change made, so the code seems to already be following the format
used by this tool.

contrib/sort.py

@@ -28,7 +28,7 @@
 
 # Requirements:
 #  python >= 3.6
-from sys import argv, exit as sys_exit
+from sys import argv, exit as sys_exit, stderr
 
 
 def sort_alphabetical(original_items):
@@ -101,13 +101,16 @@ def main(args):
             else:
                 fix_profile(filename)
         except FileNotFoundError:
-            print(f"[ Error ] Can't find `{filename}'")
+            print(f"[ Error ] Can't find `{filename}'", file=stderr)
             exit_code = 1
         except PermissionError:
-            print(f"[ Error ] Can't read/write `{filename}'")
+            print(f"[ Error ] Can't read/write `{filename}'", file=stderr)
             exit_code = 1
         except Exception as err:
-            print(f"[ Error ] An error occurred while processing `{filename}': {err}")
+            print(
+                f"[ Error ] An error occurred while processing `{filename}': {err}",
+                file=stderr,
+            )
             exit_code = 1
     return exit_code