ROSDEP

Install

sudo apt install python3-rosdep or other versions

Init

When sudo rosdep init

Terminal may say:

can not connect to https://raw.githubusercontent.com/...

Solve

First:

chmod +x rosdep.sh

Then:

./rosdep.sh

Next:

sudo rosdep init and rosdep update

Warning:

You shouldn't use some networks such as Campus Network