Add DescribeStackEvents endpoint

It returns nothing right now because there's no backend implementation
for events (yet.)

moto/cloudformation/responses.py

@@ -91,6 +91,13 @@ class CloudFormationResponse(BaseResponse):
         template = self.response_template(DESCRIBE_STACK_RESOURCES_RESPONSE)
         return template.render(stack=stack)
 
+    def describe_stack_events(self):
+        stack_name = self._get_param('StackName')
+        stack = self.cloudformation_backend.get_stack(stack_name)
+
+        template = self.response_template(DESCRIBE_STACK_EVENTS_RESPONSE)
+        return template.render(stack=stack)
+
     def list_stacks(self):
         stacks = self.cloudformation_backend.list_stacks()
         template = self.response_template(LIST_STACKS_RESPONSE)
@@ -269,6 +276,31 @@ DESCRIBE_STACK_RESOURCES_RESPONSE = """<DescribeStackResourcesResponse>
 </DescribeStackResourcesResponse>"""
 
 
+DESCRIBE_STACK_EVENTS_RESPONSE = """<DescribeStackEventsResponse xmlns="http://cloudformation.amazonaws.com/doc/2010-05-15/">
+  <DescribeStackEventsResult>
+    <StackEvents>
+      {% for event in stack.events %}
+      <member>
+        <Timestamp>{{ event.timestamp }}</Timestamp>
+        <ResourceStatus>{{ event.resource_status }}</ResourceStatus>
+        <StackId>{{ event.stack_id }}</StackId>
+        <EventId>{{ event.event_id }}</EventId>
+        <LogicalResourceId>{{ event.logical_resource_id }}</LogicalResourceId>
+        {% if event.resource_status_reason %}<ResourceStatusReason>{{ event.resource_status_reason }}</ResourceStatusReason>{% endif %}
+        <StackName>{{ event.stack_name }}</StackName>
+        <PhysicalResourceId>{{ event.physical_resource_id }}</PhysicalResourceId>
+        {% if event.resource_properties %}<ResourceProperties>{{ event.resource_properties }}</ResourceProperties>{% endif %}
+        <ResourceType>{{ event.resource_type }}</ResourceType>
+      </member>
+      {% endfor %}
+    </StackEvents>
+  </DescribeStackEventsResult>
+  <ResponseMetadata>
+    <RequestId>b9b4b068-3a41-11e5-94eb-example</RequestId>
+  </ResponseMetadata>
+</DescribeStackEventsResponse>"""
+
+
 LIST_STACKS_RESPONSE = """<ListStacksResponse>
  <ListStacksResult>
   <StackSummaries>