Added upgrade impact section

It is necessary to have such a section
in order to enforce developer to describe
how a proposed change can influence upgrade
process or any features which are currently
supported.

Change-Id: I0000e8a592b50315b5a9107312ffaa49ec10c837

specs/5.1/fake.rst

@@ -35,6 +35,11 @@ REST API impact
 
 None
 
+Upgrade impact
+--------------
+
+None
+
 Security impact
 ---------------
 

specs/template.rst

@@ -125,6 +125,15 @@ Each API method which is either added or changed should have the following
 * Discuss any policy changes, and discuss what things a deployer needs to
   think about when defining their policy.
 
+Upgrade impact
+--------------
+
+If this change set concerns any kind of upgrade process, describe how it is
+supposed to deal with that stuff. For example, Fuel currently supports
+upgrading of master node, so it is necessary to describe whether this patch
+set contradicts upgrade process itself or any working feature that we need
+to support.
+
 Security impact
 ---------------
 

tests/test_titles.py

@@ -52,6 +52,7 @@ class TestTitles(testtools.TestCase):
         self.assertIn('Alternatives', titles[proposed])
         self.assertIn('Data model impact', titles[proposed])
         self.assertIn('REST API impact', titles[proposed])
+        self.assertIn('Upgrade impact', titles[proposed])
         self.assertIn('Security impact', titles[proposed])
         self.assertIn('Notifications impact', titles[proposed])
         self.assertIn('Other end user impact', titles[proposed])