Add script for objetive error observer

src/rosgraph_monitor/observers/objetive_error_observer.py

@@ -0,0 +1,27 @@
+from rosgraph_monitor.observer import TopicObserver
+from std_msgs.msg import Bool
+from diagnostic_msgs.msg import DiagnosticStatus, KeyValue
+
+
+class ObjetiveErrorObserver(TopicObserver):
+    def __init__(self, name):
+        topics = [("/obj_error", Bool)]     # list of pairs
+
+        super(ObjetiveErrorObserver, self).__init__(
+            name, 10, topics)
+
+    def calculate_attr(self, msgs):
+        status_msg = DiagnosticStatus()
+
+        attr = str("False")
+        if msgs[0].data:
+            attr = str("True")
+
+        status_msg = DiagnosticStatus()
+        status_msg.level = DiagnosticStatus.OK
+        status_msg.name = self._id
+        status_msg.values.append(
+            KeyValue("objetive_error", attr))
+        status_msg.message = "QA status"
+
+        return status_msg