Fix for KeyError when cache is empty, change cache key prefix for dev vs. prod.

Conflicts:
	awx/settings/production.py

awx/main/models/inventory.py

@@ -300,7 +300,7 @@ class Host(CommonModelNameNotUnique):
             if summary_data[key] is None:
                 rebuild_cache = True
                 break
-        if rebuild_cache:
+        if rebuild_cache or not summary_data:
             summary_data = self.update_cached_values()
         summary_data_actual = dict(all_groups=summary_data['%s_all_groups' % self.id],
                                    groups=summary_data['%s_groups' % self.id],

awx/settings/defaults.py

@@ -229,6 +229,7 @@ CACHES = {
         'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
         'LOCATION': '127.0.0.1:11211',
         'TIMEOUT': 864000,
+        'KEY_PREFIX': 'tower_dev',
     }
 }
 

awx/settings/production.py

@@ -43,6 +43,9 @@ JOBOUTPUT_ROOT = '/var/lib/awx/job_status/'
 # The heartbeat file for the tower scheduler
 SCHEDULE_METADATA_LOCATION = '/var/lib/awx/.tower_cycle'
 
+# Use different cache prefix for production vs. development.
+CACHES['default']['KEY_PREFIX'] = 'tower'
+
 LOGGING['handlers']['rotating_file'] = {
     'level': 'WARNING',
     'class':'logging.handlers.RotatingFileHandler',