Doesn't fail if host has NO SRV record

Just catch an other exception type coming from the dns resolver that
could be raised with hosts like "anon.example.com" which just don't have
any SRV record.

sleekxmpp/clientxmpp.py

@@ -164,7 +164,7 @@ class ClientXMPP(BaseXMPP):
                 try:
                     xmpp_srv = "_xmpp-client._tcp.%s" % self.server
                     answers = dns.resolver.query(xmpp_srv, dns.rdatatype.SRV)
-                except dns.resolver.NXDOMAIN:
+                except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
                     log.debug("No appropriate SRV record found." + \
                                   " Using JID server name.")
                 else: