Several code simplifications

src/UsersDetails.py

@@ -357,10 +357,10 @@ class UsersDetails:
         etc_passwd_lines, user_group_names, user_group_ids = Users.users_groups_func()
 
         # Get all user process PIDs and elapsed times (seconds) since they are started.
+        command_list = ["ps", "--no-headers", "-eo", "pid,etimes,user"]
         if Config.environment_type == "flatpak":
-            ps_output_lines = (subprocess.check_output(["flatpak-spawn", "--host", "ps", "--no-headers", "-eo", "pid,etimes,user"], shell=False)).decode().strip().split("\n")
-        else:
-            ps_output_lines = (subprocess.check_output(["ps", "--no-headers", "-eo", "pid,etimes,user"], shell=False)).decode().strip().split("\n")
+            command_list = ["flatpak-spawn", "--host"] + command_list
+        ps_output_lines = (subprocess.run(command_list, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE)).stdout.decode().strip().split("\n")
 
         # Get user process PIDs, logged in users and user start times.
         pid_list = []