title: i can't install docker on ubuntu 17.10
body: <p>i'am trying to install Docker on my ubuntu 17.10 so  i followed the instructions on the link : 
  <a href="https://i.stack.imgur.com/UG2oo.png" rel="nofollow noreferrer">https://docs.docker.com/install/linux/docker-ce/ubuntu/</a></p>
  
  <pre><code> sudo apt-get update
  </code></pre>
  
  <p>it shows <a href="https://i.stack.imgur.com/UG2oo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UG2oo.png" alt="enter image description here"></a></p>
  
  <pre><code>sudo apt-get install \
  apt-transport-https \
  ca-certificates \
  curl \
  gnupg-agent \
  software-properties-common
  </code></pre>
  
  <p>shows 
  <a href="https://i.stack.imgur.com/m360M.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/m360M.png" alt="enter image description here"></a></p>
  
  <p><strong>what can i do please ?</strong></p>