MongoDB ServerSelectionTimeoutError: Nenhum servidor encontrado ainda

Question

Eu tenho uma instância do mongodb sendo executada em um servidor AWS Ubuntu 14.04 padrão. Depois de algum problema (atualizando o servidor usando sudo mongod --upgrade --dbpath /var/lib/mongodb/ ) agora tenho o servidor em execução, mas ao tentar conectar-me a ele do meu código Python, recebo um ServerSelectionTimeoutError: No servers found yet .

Eu reiniciei o mongodb com sudo service mongodb restart e verifiquei os logs:

Wed Dec 23 15:15:14.571 [initandlisten] MongoDB starting : pid=21554 port=27017 dbpath=/var/lib/mongodb 64-bit host=ip-172-31-29-10
Wed Dec 23 15:15:14.571 [initandlisten] db version v2.4.9
Wed Dec 23 15:15:14.571 [initandlisten] git version: nogitversion
Wed Dec 23 15:15:14.571 [initandlisten] build info: Linux orlo 3.2.0-58-generic #88-Ubuntu SMP Tue Dec 3 17:37:58 UTC 2013 x86_64 BOOST_LIB_VERSION=1_54
Wed Dec 23 15:15:14.571 [initandlisten] allocator: tcmalloc
Wed Dec 23 15:15:14.571 [initandlisten] options: { bind_ip: "127.0.0.1", config: "/etc/mongodb.conf", dbpath: "/var/lib/mongodb", journal: "true", logappend: "true", logpath: "/var/log/mongodb/mongodb.log" }
Wed Dec 23 15:15:14.575 [initandlisten] journal dir=/var/lib/mongodb/journal
Wed Dec 23 15:15:14.575 [initandlisten] recover : no journal files present, no recovery needed
Wed Dec 23 15:15:14.593 [initandlisten] waiting for connections on port 27017
Wed Dec 23 15:15:14.593 [websvr] admin web console waiting for connections on port 28017
Wed Dec 23 15:15:15.337 [initandlisten] connection accepted from 127.0.0.1:45356 #1 (1 connection now open)
Wed Dec 23 15:15:15.850 [conn1] end connection 127.0.0.1:45356 (0 connections now open)
Wed Dec 23 15:15:16.191 [initandlisten] connection accepted from 127.0.0.1:45360 #2 (1 connection now open)
Wed Dec 23 15:15:16.788 [conn2] end connection 127.0.0.1:45360 (0 connections now open)
Wed Dec 23 15:15:17.130 [initandlisten] connection accepted from 127.0.0.1:45364 #3 (1 connection now open)
Wed Dec 23 15:15:18.108 [conn3] end connection 127.0.0.1:45364 (0 connections now open)
Wed Dec 23 15:15:18.439 [initandlisten] connection accepted from 127.0.0.1:45368 #4 (1 connection now open)
Wed Dec 23 15:15:18.934 [conn4] end connection 127.0.0.1:45368 (0 connections now open)
etc. 
etc. 

Não consigo encontrar nenhuma informação sobre o fechamento imediato de conexões.

Alguém tem alguma idéia de como eu poderia resolver isso? Estou batendo minha cabeça contra a parede aqui, então todas as dicas são bem vindas!