The old slack webhook API still works. It's just deprecated by slack.

Analyze the given token and use the old webhook format if the token
is old style and use the new format if the token is new style.  Make
domain optional with new-style tokens.

Fixes #157

notification/slack.py

@@ -28,12 +28,20 @@ author: Ramon de la Fuente <ramon@delafuente.nl>
 options:
   domain:
     description:
-      - Slack (sub)domain for your environment without protocol.
-        (i.e. C(future500.slack.com))
-    required: true
+      - Slack (sub)domain for your environment without protocol. (i.e.
+        C(future500.slack.com)) In 1.8 and beyond, this is deprecated and may
+        be ignored.  See token documentation for information.
+    required: false
   token:
     description:
-      - Slack integration token
+      - Slack integration token.  This authenticates you to the slack service.
+        Prior to 1.8, a token looked like C(3Ffe373sfhRE6y42Fg3rvf4GlK).  In
+        1.8 and above, ansible adapts to the new slack API where tokens look
+        like C(G922VJP24/D921DW937/3Ffe373sfhRE6y42Fg3rvf4GlK).  If tokens
+        are in the new format then slack will ignore any value of domain.  If
+        the token is in the old format the domain is required.  Ansible has no
+        control of when slack will get rid of the old API.  When slack does
+        that the old format will stop working.
     required: true
   msg:
     description:
@@ -105,6 +113,7 @@ EXAMPLES = """
 
 """
 
+OLD_SLACK_INCOMING_WEBHOOK = 'https://%s/services/hooks/incoming-webhook?token=%s'
 SLACK_INCOMING_WEBHOOK = 'https://hooks.slack.com/services/%s'
 
 def build_payload_for_slack(module, text, channel, username, icon_url, icon_emoji, link_names, parse):
@@ -127,7 +136,13 @@ def build_payload_for_slack(module, text, channel, username, icon_url, icon_emoj
     return payload
 
 def do_notify_slack(module, domain, token, payload):
+    if token.count('/') >= 2:
+        # New style token
         slack_incoming_webhook = SLACK_INCOMING_WEBHOOK % (token)
+    else:
+        if not domain:
+            module.fail_json(msg="Slack has updated its webhook API.  You need to specify a token of the form XXXX/YYYY/ZZZZ in your playbook")
+        slack_incoming_webhook = OLD_SLACK_INCOMING_WEBHOOK % (domain, token)
 
     response, info = fetch_url(module, slack_incoming_webhook, data=payload)
     if info['status'] != 200:
@@ -137,7 +152,7 @@ def do_notify_slack(module, domain, token, payload):
 def main():
     module = AnsibleModule(
         argument_spec = dict(
-            domain      = dict(type='str', required=True),
+            domain      = dict(type='str', required=False, default=None),
             token       = dict(type='str', required=True),
             msg         = dict(type='str', required=True),
             channel     = dict(type='str', default=None),