Revert dnspython to 1.x

src/pretix/control/views/mailsetup.py

@@ -42,7 +42,8 @@ logger = logging.getLogger(__name__)
 
 def get_spf_record(hostname):
     try:
-        for resp in dns.resolver.resolve(hostname, 'TXT'):
+        r = dns.resolver.Resolver()
+        for resp in r.query(hostname, 'TXT'):
             data = b''.join(resp.strings).decode()
             if data.lower().strip().startswith('v=spf1 '):  # RFC7208, section 4.5
                 return data