Merge remote-tracking branch 'tower/release_3.2.3' into devel

* tower/release_3.2.3:
  fix unicode bugs with log statements
  use --export option for ansible-inventory
  add support for new "BECOME" prompt in Ansible 2.5+ for adhoc commands
  enforce strings for secret password inputs on Credentials
  fix a bug for "users should be able to change type of unused credential"
  fix xss vulnerabilities - on host recent jobs popover - on schedule name tooltip
  fix a bug when testing UDP-based logging configuration
  bump templates form credential_types page limit
  Wait for Slack RTM API websocket connection to be established
  don't process artifacts from custom `set_stat` calls asynchronously
  don't overwrite env['ANSIBLE_LIBRARY'] when fact caching is enabled
  only allow facts to cache in the proper file system location
  replace our memcached-based fact cache implementation with local files
  add support for new "BECOME" prompt in Ansible 2.5+
  fix a bug in inventory generation for isolated nodes
  properly handle unicode for isolated job buffers

awx/main/notifications/slack_backend.py

@@ -1,6 +1,7 @@
 # Copyright (c) 2016 Ansible, Inc.
 # All Rights Reserved.
 
+import time
 import logging
 from slackclient import SlackClient
 
@@ -9,6 +10,7 @@ from django.utils.translation import ugettext_lazy as _
 from awx.main.notifications.base import AWXBaseEmailBackend
 
 logger = logging.getLogger('awx.main.notifications.slack_backend')
+WEBSOCKET_TIMEOUT = 30
 
 
 class SlackBackend(AWXBaseEmailBackend):
@@ -30,7 +32,18 @@ class SlackBackend(AWXBaseEmailBackend):
         if not self.connection.rtm_connect():
             if not self.fail_silently:
                 raise Exception("Slack Notification Token is invalid")
-        return True
+
+        start = time.time()
+        time.clock()
+        elapsed = 0
+        while elapsed < WEBSOCKET_TIMEOUT:
+            events = self.connection.rtm_read()
+            if any(event['type'] == 'hello' for event in events):
+                return True
+            elapsed = time.time() - start
+            time.sleep(0.5)
+
+        raise RuntimeError("Slack Notification unable to establish websocket connection after {} seconds".format(WEBSOCKET_TIMEOUT))
 
     def close(self):
         if self.connection is None: