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

src/setup.py

@@ -190,7 +190,7 @@ setup(
         'django-scopes==1.2.*',
         'django-statici18n==2.1.*',
         'djangorestframework==3.12.*',
-        'dnspython==2.2.*',
+        'dnspython<2.0',  # do not upgrade, causes issues with eventlet / gunicorn 19 and we cannot upgrade gunicorn right now
         'drf_ujson2==1.6.*',
         'isoweek',
         'jsonschema',