Hello, I'm troubled in install ROS lunar on Ubuntu 16.04, when I try rosdep update, this is what it shows:

$ rosdep update
reading in sources list data from /etc/ros/rosdep/sources.list.d
Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/osx-homebrew.yaml
Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/base.yaml
Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/python.yaml
Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/ruby.yaml
Hit https://raw.githubusercontent.com/ros/rosdistro/master/releases/fuerte.yaml
Query rosdistro index https://raw.githubusercontent.com/ros/rosdistro/master/index.yaml
Add distro "groovy"
ERROR: error loading sources list:
    ('The read operation timed out',)

OS:

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.3 LTS
Release:    16.04
Codename:   xenial

rosdep:

$ rosdep --version
0.11.8

manually wgetting:

$ wget https://raw.githubusercontent.com/ros/rosdistro/master/index.yaml
--2017-12-06 09:39:13--  https://raw.githubusercontent.com/ros/rosdistro/master/index.yaml
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 151.101.72.133
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|151.101.72.133|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 973 [text/plain]
Saving to: ‘index.yaml’

index.yaml          100%[===================>]     973  --.-KB/s    in 0s      

2017-12-06 09:39:14 (177 MB/s) - ‘index.yaml’ saved [973/973]

I think it's not network problem. with wget is OK, only rosdep update is NOT OK. Would you help me?