You can clone with
HTTPS or Subversion.
It's a problem with Socket.io-client and was discussed in here: Automattic/socket.io-client#490
I tried to manually remove the AMD support from the Socket.io-client and then it works.
But now I want to deploy it on Heroku. The Socket.io-client is automatically installed so that I could not modify it. I am wondering whether it can be solved? Thank you!