Make new constant: CALL_REPORT_KEYS

Make a new constant: `pulp_smash.constants.CALL_REPORT_KEYS`. Update code base
by referencing this single constant and dropping other private declarations of
the call report keys.

Test suite results do not change when run against either Pulp 2.6 or 2.7, on
either Python 2 or 3.

pulp_smash/constants.py

@@ -3,6 +3,15 @@
 from __future__ import unicode_literals
 
 
+CALL_REPORT_KEYS = frozenset(('error', 'result', 'spawned_tasks'))
+"""See: `Call Report`_.
+
+.. _Call Report:
+    http://pulp.readthedocs.org/en/latest/dev-guide/conventions/sync-v-async.html#call-report
+
+"""
+
+
 ERROR_KEYS = frozenset((
     '_href',
     'error',

pulp_smash/tests/platform/api_v2/test_content_applicability.py

@@ -9,9 +9,9 @@
 
 import requests
 from pulp_smash.config import get_config
+from pulp_smash.constants import CALL_REPORT_KEYS
 from unittest2 import TestCase
 
-_CALL_REPORT_KEYS = {'error', 'result', 'spawned_tasks'}
 _CONSUMER = '/pulp/api/v2/consumers/actions/content/regenerate_applicability/'
 _REPO = '/pulp/api/v2/repositories/actions/content/regenerate_applicability/'
 
@@ -47,8 +47,8 @@ def test_body(self):
         for i, response in enumerate(self.responses):
             with self.subTest(i):
                 self.assertEqual(
-                    set(response.json().keys()),
-                    _CALL_REPORT_KEYS,
+                    frozenset(response.json().keys()),
+                    CALL_REPORT_KEYS,
                 )
 
 
@@ -82,4 +82,7 @@ def test_body(self):
         """Assert that the responses are JSON and appear to be call reports."""
         for i, resp in enumerate(self.responses):
             with self.subTest(i):
-                self.assertNotEqual(set(resp.json().keys()), _CALL_REPORT_KEYS)
+                self.assertNotEqual(
+                    frozenset(resp.json().keys()),
+                    CALL_REPORT_KEYS,
+                )

pulp_smash/tests/rpm/api_v2/test_sync_publish.py

@@ -35,6 +35,7 @@
 import os
 import requests
 from pulp_smash.config import get_config
+from pulp_smash.constants import CALL_REPORT_KEYS
 from pulp_smash.utils import (
     create_repository,
     delete,
@@ -512,8 +513,8 @@ def test_call_reports_keys(self):
         for step in {'import', 'copy', 'publish'}:
             with self.subTest(step=step):
                 self.assertEqual(
-                    set(self.bodies[step].keys()),
-                    {'error', 'result', 'spawned_tasks'},
+                    frozenset(self.bodies[step].keys()),
+                    CALL_REPORT_KEYS,
                 )
 
     def test_call_reports_values(self):