certbot certonly --manual --manual-auth-hook /etc/letsencrypt/acme-dns-auth.py --preferred-challenges dns --debug-challenges -d *.mydomain.ch

acme-dns-auth.py

#!/usr/bin/env python
import json
import os
import requests
import sys
from requests.auth import HTTPBasicAuth

# URL to acme-dns instance
ACMEDNS_URL = ""
ACMEDNS_DOMAIN = ""
ACMEDNS_USER = ""
ACMEDNS_PASS = ""

###   DO NOT EDIT BELOW THIS POINT   ###
###         HERE BE DRAGONS          ###

VALIDATION_TOKEN = os.environ["CERTBOT_VALIDATION"]


class AcmeDnsClient(object):
    """
    Handles the communication with ACME-DNS API
    """

    def __init__(self, acmedns_url):
        self.acmedns_url = acmedns_url

    def update_txt_record(self, txt):
        """Updates the TXT challenge record to ACME-DNS subdomain."""

        print("Update TXT challenge to " + txt)

        update = {"type": "TXT", "hostname": ACMEDNS_DOMAIN, "token": txt}
        headers = {"Content-Type": "application/json"}
        res = requests.post(self.acmedns_url+"/update",
                            headers=headers,
                            auth=(ACMEDNS_USER, ACMEDNS_PASS),
                            data=json.dumps(update))

        if res.status_code == 200:
            return
        else:
            sys.exit(1)

if __name__ == "__main__":
    # Init
    client = AcmeDnsClient(ACMEDNS_URL)

    # Update the TXT record in acme-dns instance
    client.update_txt_record(VALIDATION_TOKEN)