Fix lint issues.

acme/acme/challenges.py

@@ -599,4 +599,3 @@ class DNSResponse(ChallengeResponse):
 
         """
         return chall.check_validation(self.validation, account_public_key)
-

acme/acme/dns_resolver.py

@@ -8,6 +8,7 @@ import dns.exception
 
 logger = logging.getLogger(__name__)
 
+
 def txt_records_for_name(name):
     """Resolve the name and return the TXT records.