Fix exception that is not properly raised

This commit fixes an exception that was not properly raised, and
also makes the exception more relevant.

This also fixes an outstanding bug where, if the agent
was not associated with a node, get_node_uuid() would fail in an
unexpected manner.

Change-Id: Ifca474a73dd50b5fd2242e5b7e938a5db04f27a8

ironic_python_agent/agent.py

@@ -181,8 +181,8 @@ class IronicPythonAgent(base.ExecuteCommandMixin):
             return iface_list
 
     def get_node_uuid(self):
-        if 'uuid' not in self.node:
-            errors.HeartbeatError('Tried to heartbeat without node UUID.')
+        if self.node is None or 'uuid' not in self.node:
+            raise errors.UnknownNodeError()
         return self.node['uuid']
 
     def list_command_results(self):

ironic_python_agent/errors.py

@@ -236,3 +236,14 @@ class VirtualMediaBootError(RESTError):
 
 class ExtensionError(Exception):
     pass
+
+
+class UnknownNodeError(Exception):
+    """Error raised when the agent is not associated with an Ironic node."""
+
+    message = 'Agent is not associated with an Ironic node.'
+
+    def __init__(self, message=None):
+        if message is not None:
+            self.message = message
+        super(UnknownNodeError, self).__init__(self.message)

ironic_python_agent/tests/agent.py

@@ -284,6 +284,19 @@ class TestBaseAgent(test_base.BaseTestCase):
 
         self.assertEqualEncoded(result, expected_result)
 
+    def test_get_node_uuid(self):
+        self.agent.node = {'uuid': 'fake-node'}
+        self.assertEqual('fake-node', self.agent.get_node_uuid())
+
+    def test_get_node_uuid_unassociated(self):
+        self.assertRaises(errors.UnknownNodeError,
+                          self.agent.get_node_uuid)
+
+    def test_get_node_uuid_invalid_node(self):
+        self.agent.node = {}
+        self.assertRaises(errors.UnknownNodeError,
+                          self.agent.get_node_uuid)
+
 
 class TestAgentCmd(test_base.BaseTestCase):
     @mock.patch('ironic_python_agent.openstack.common.log.getLogger')