wee-slack: Cannot connect to Slack: "Error (code 0): ratelimited"

Today I cannot log into Slack through weechat/wee-slack. The following error is presented:

Failed requesting rtm.connect with token
xoxc-[redacted], retrying. If this persists, try
increasing slack_timeout. Error (code 0): ratelimited

Two attempts are made at 60-second intervals, after which the message becomes:

Failed requesting rtm.connect with token
xoxc-[redacted], will not retry after too many failed 
attempts. If this persists, try increasing slack_timeout. 
Error (code 0): ratelimited

and nothing else happens.

Things that I’ve tried but didn’t help:

• Getting a new token
• Updating to the latest update with commit c303a77 (“Include cookie when making the websocket connection”)
• Changing slack_timeout to 90000
• Switching my outbound IP address (my WiFi and wired connections use different ISPs)

I added the following change so I could see the value of retry_after:

$ git diff
diff --git a/wee_slack.py b/wee_slack.py
index 84c437f..b0e5e5d 100644
--- a/wee_slack.py
+++ b/wee_slack.py
@@ -680,7 +680,7 @@ class EventRouter(object):
                 if name.lower() == "retry-after":
                     retry_after = int(value.strip())
                     request_metadata.retry_time = time.time() + retry_after
-                    return "", "ratelimited"
+                    return "", "ratelimited, retry after "+str(retry_after)+"s"
 
         return body, ""

The new message indicated that retry_after is 60 seconds.