title: CMake installation issue on raspbian stretch
body: <p>im having some troubles installing CMake on raspberry pi 3 running raspbian stretch. </p>
  
  <p>I keep getting this error message when i run the command </p>
  
  <pre><code>sudo apt-get install build-essential cmake pkg-config
  </code></pre>
  
  <p>The error message: </p>
  
  <pre><code>&gt; " Reading package lists... Done  Building dependency tree Reading
  &gt; state information... Done  Package CMake is not available, but is
  &gt; referred to by another package. This may mean that the package is
  &gt; missing, has been obsoleted, or  is only available from another source
  &gt; 
  &gt; E: Package 'cmake' has no installation candidate "
  </code></pre>
  
  <p>I've tried other installation methods like "<code>pip install cmake</code>" &amp; "<code>sudo apt-get install -y cmake</code>" but all to no avail. Could you guys help me out? Is there a library i can extract from?</p>
  
  <p>Thank you in advance.</p>
  
  <p>Im running raspbian stretch 2018-03-13 installed on raspberry pi 3.</p>