Fixes an issue where fab doesn't work for some setups

This is an issue I ran into during setup a while ago. 

Using fab load_db_dump or open_db or whatever doesn't work if the file insecure_private_key (which use_vagrant() searches for in fabfile.py) was installed in a location with a space in the directory path. In particular (at least on Windows), local('cd ../vagrant && vagrant ssh-config | grep IdentityFile', capture=True) returns something of the form:

IdentityFile path/to/insecure_private_key

so splitting and taking the index-1 element makes sense, but if the path contains a space, it'll return something like

IdentityFile "path/to/the file/insecure_private_key"

so I split exactly once, take the index-1 element, and strip the quotes. 

I haven't tested this on another machine, but it should work the same as before if the problem I'm addressing is irrelevant to you.
Leaving in the print statement adds clutter, so it would be better to take this out now that you've fixed the issue.