Merge ~nteodosio/software-properties:threading into software-properties:ubuntu/master

[Nathan Teodosio]

GLib.Thread is not available in Bionic and Focal: https://gitlab.gnome.org/GNOME/glib/-/issues/602.

Use Python threading module.

Also need to let daemonic threads go lest software-properties becomes uncloseable after invoking the UA attach dialog without subsequent verification of the PIN in the magic attach flow.

That, in my reading, is backed up by the definition of daemonic thread[1]:

> A thread can be flagged as a “daemon thread”. The significance of this flag is that the entire Python program exits when only daemon threads are left.

[1]: https://docs.python.org/3/library/threading.html

[Nathan Teodosio (nteodosio)]

For the record, this was merged in Bionic only: https://git.launchpad.net/software-properties/commit/?id=5f7360ce3aaf893146885029946b3bc8a8b2c9ed

diff --git a/softwareproperties/SoftwareProperties.py b/softwareproperties/SoftwareProperties.py
index 835a1c6..9e94fa6 100644
--- a/softwareproperties/SoftwareProperties.py
+++ b/softwareproperties/SoftwareProperties.py
@@ -128,7 +128,8 @@ class SoftwareProperties(object):
     " wait for all running threads (PPA key fetchers) to exit "
     for t in threading.enumerate():
       if t.ident != threading.current_thread().ident:
-        t.join()
+        if not t.daemon:
+            t.join()
 
   def backup_apt_conf(self):
     """Backup all apt configuration options"""
diff --git a/softwareproperties/gtk/DialogUaAttach.py b/softwareproperties/gtk/DialogUaAttach.py
index 221def4..20bb543 100644
--- a/softwareproperties/gtk/DialogUaAttach.py
+++ b/softwareproperties/gtk/DialogUaAttach.py
@@ -25,6 +25,7 @@ from softwareproperties.gtk.utils import setup_ui
 from uaclient.api.u.pro.attach.magic.initiate.v1 import initiate
 from uaclient.api.u.pro.attach.magic.wait.v1 import MagicAttachWaitOptions, wait
 from uaclient.exceptions import MagicAttachTokenError
+import threading
 
 class DialogUaAttach:
     def __init__(self, parent, datadir, ua_object):
@@ -135,8 +136,6 @@ class DialogUaAttach:
         self.attach()
 
     def on_cancel_clicked(self, button):
-        if self.poll:
-            GLib.Thread.unref(self.poll)
         self.dialog.response(Gtk.ResponseType.CANCEL)
 
     def poll_for_magic_token(self):
@@ -168,7 +167,7 @@ class DialogUaAttach:
             print(e)
             return
         self.update_state()
-        self.poll = GLib.Thread.new("poll", self.poll_for_magic_token)
+        threading.Thread(target=self.poll_for_magic_token, daemon=True).start()
 
     def on_radio_toggled(self, button):
         self.update_state()