export_for_nextstrain.smk: catch Slack errors

The Slack messages are just a nice-to-have feature and should not cause the entire workflow to crash if there is an error. Prompted by <#1173 (comment)>

Author: joverlee521

workflow/snakemake_rules/export_for_nextstrain.smk

@@ -439,9 +439,12 @@ def send_slack_message(message, broadcast=False):
 exceptNoSuchEntryError:
 pass
 
-response=requests.post("https://slack.com/api/chat.postMessage", headers=headers, data=json.dumps(data))
-response.raise_for_status()
-storage.store_if_not_present("slack_thread_ts", response.json()["ts"])
+try:
+response=requests.post("https://slack.com/api/chat.postMessage", headers=headers, data=json.dumps(data))
+response.raise_for_status()
+storage.store_if_not_present("slack_thread_ts", response.json()["ts"])
+exceptExceptionaserror:
+print("An error occurred when sending Slack message:", error)
 
 # onstart handler will be executed before the workflow starts.
 onstart: