Solves the "TypeError: 'NoneType' object is not iterable" when getting nodetemplate relationships.

Closes-Bug: #1527214

Change-Id: Ibf5ecb0cc5a600387ef98603087abab084741211

toscaparser/nodetemplate.py

@@ -102,13 +102,14 @@ class NodeTemplate(EntityTemplate):
             if relationship:
                 found_relationship_tpl = False
                 # apply available relationship templates if found
-                for tpl in self.available_rel_tpls:
-                    if tpl.name == relationship:
-                        rtype = RelationshipType(tpl.type, None,
-                                                 self.custom_def)
-                        explicit_relation[rtype] = related_tpl
-                        self.relationship_tpl.append(tpl)
-                        found_relationship_tpl = True
+                if self.available_rel_tpls:
+                    for tpl in self.available_rel_tpls:
+                        if tpl.name == relationship:
+                            rtype = RelationshipType(tpl.type, None,
+                                                     self.custom_def)
+                            explicit_relation[rtype] = related_tpl
+                            self.relationship_tpl.append(tpl)
+                            found_relationship_tpl = True
                 # create relationship template object.
                 rel_prfx = self.type_definition.RELATIONSHIP_PREFIX
                 if not found_relationship_tpl:

toscaparser/tests/data/test_available_rel_tpls.yaml

@@ -0,0 +1,23 @@
+tosca_definitions_version: tosca_simple_yaml_1_0
+
+description: TOSCA test for bug 1527214
+
+topology_template:
+
+  node_templates:
+
+    test_db:
+      type: tosca.nodes.Database
+      requirements:
+        - host:
+            node: mysql
+
+    mysql:
+      type: tosca.nodes.DBMS
+      requirements:
+        - host:
+            node: db_server
+
+    db_server:
+      type: tosca.nodes.Compute
+

toscaparser/tests/test_toscatpl.py

@@ -544,3 +544,15 @@ class ToscaTemplateTest(TestCase):
             "data/CSAR/csar_elk.csar")
         tosca = ToscaTemplate(tosca_tpl)
         self.assertTrue(tosca.topology_template.custom_defs)
+
+    def test_available_rel_tpls(self):
+        tosca_tpl = os.path.join(
+            os.path.dirname(os.path.abspath(__file__)),
+            "data/test_available_rel_tpls.yaml")
+        tosca = ToscaTemplate(tosca_tpl)
+        for node in tosca.nodetemplates:
+            for relationship, target in node.relationships.items():
+                try:
+                    target.relationships
+                except TypeError as error:
+                    self.fail(error)