我正在尝试从 github 获取 nova 代码，但出现以下错误：
#git clone https://github.com/openstack/nova.git
Initialized empty Git repository in /home/avikki/Desktop/nt/nova/.git/
error: Failed connect to github.com:443; Operation now in progress while accessing https://github.com/openstack/nova.git/info/refs
fatal: HTTP request failed
你能建议怎么做吗？