Only use systemd notify when NOTIFY_SOCKET is set

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>

main.py

@@ -54,7 +54,9 @@ class PodKeeper:
         print(f"Starting pod {self.podname} at {last_check}", file=sys.stderr, flush=True)
         podman.play.kube(self.podyaml, *self.podnet_args)
         try:
-            sdnotify("--ready")
+            if 'NOTIFY_SOCKET' in os.environ:
+                sdnotify("--ready")
+
             while not self.stopping.is_set():
                 self.waiter.wait()
                 self.waiter.clear()