fix old git compatibility issue

src/rpi-cpu2mqtt.py

@@ -145,8 +145,12 @@ def get_manufacturer():
 def check_git_update():
     script_dir = os.path.dirname(os.path.realpath(__file__))
     full_cmd = "git -C {} remote update && git -C {} status -uno".format(script_dir, script_dir)
-    git_update = subprocess.Popen(full_cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()[0].decode("utf-8")
-    if 'Your branch is up to date' in git_update:
+    try:
+        git_update = subprocess.Popen(full_cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()[0].decode("utf-8")
+    except subprocess.CalledProcessError as e:
+        print("Error updating git repository:", e.output)
+
+    if any(s in git_update for s in ('Your branch is up to date', 'Your branch is up-to-date')):
         git_update = 'off'
     else:
         git_update = 'on'