Open a Terminal and type curl and see if it gives you a positive answer. If you don't have the curl libraries maybe it's best to continue with pywallet
If you have curl, maybe you want to try this, instead of installing more stuff. Even if you don't have curl and won't use it, maybe it will be useful to someone else
Open your bitcoin.conf file and put this inside
rpcpassword=
server=1
Start Bitcoin-qt in the normal way and it will start as a server.
Open a Terminal and type
replace
Press enter. It will prompt you for the password you set on the bitcoin.conf file. Write it and press enter.
Voilá, it will answer with the private key for the address.
Repeat the Terminal steps for each address.