Adjust subprocess calls to use new text arg in addvgridowner reusing the

similar update to the shared vgrid module in PR292 and syncing minor bits while
at it.

Untested in practice so not ready for merge, yet.

Follow-up to issue #288.

Author: jonasbardino

mig/shared/functionality/addvgridowner.py

@@ -4,7 +4,7 @@
 # --- BEGIN_HEADER ---
 #
 # addvgridowner - add one or more vgrid owners
-# Copyright (C) 2003-2023  The MiG Project lead by Brian Vinter
+# Copyright (C) 2003-2025  The MiG Project by the Science HPC Center at UCPH
 #
 # This file is part of MiG.
 #
@@ -90,13 +90,15 @@ def add_tracker_admin(configuration, cert_id, vgrid_name, tracker_dir,
                      'permission', 'add', admin_id, 'TRAC_ADMIN']
         _logger.info('provide admin rights to owner: %s' % perms_cmd)
         # NOTE: We already verified command variables to be shell-safe
+        # NOTE: we want utf8-encoded output as text str for find below
         proc = subprocess_popen(perms_cmd, stdout=subprocess_pipe,
-                                stderr=subprocess_stdout, env=admin_env)
-        proc.wait()
-        if proc.returncode != 0:
+                                stderr=subprocess_stdout, text=True,
+                                env=admin_env)
+        retval = proc.wait()
+        if retval != 0:
+            out = proc.stdout.read()
             raise Exception("tracker permissions %s failed: %s (%d)" %
-                            (perms_cmd, proc.stdout.read(),
-                             proc.returncode))
+                            (perms_cmd, out, retval))
         return True
     except Exception as exc:
         _logger.error("failed to give %s tracker admin rights: %s" % (cert_id,