make develop fails

[iconofsin]

When I run `make develop' (CentOS 6.4 x86_64) with the latest hinge cloned off of github, at some point make produces the following:

make[1]: Entering directory `/home/icon/tools/hinge/vendor'
=> Updating submodules
(cd .. ; git submodule update --init --recursive;)
Initialized empty Git repository in /home/icon/tools/hinge/vendor/cl-ev/.git/
Warning: Permanently added the RSA host key for IP address '192.30.252.131' to the list of known hosts.
Permission denied (publickey).
fatal: The remote end hung up unexpectedly
Clone of 'git@github.com:sshirokov/cl-ev.git' into submodule path 'vendor/cl-ev' failed
make[1]: *** [init] Error 1
make[1]: Leaving directory `/home/icon/tools/hinge/vendor'
make: *** [init] Error 2

I'm not sure if this is an issue with hinge or something else, but I can ping the stated address and I can clone cl-ev manually into vendors/cl-ev, after which rerunning `make develop' finishes successfully with 'You should be good to go'.