title: Problems when installing python3-dev
body: <p>This problem has been torturing me for 2 days, and without <code>python3-dev</code> I can't pip install any module, can someone tell how could I solve this?  </p>
  
  <pre><code>The following packages have unmet dependencies:
       python3-dev : Depends: python3 (= 3.5.1-3) but 3.5.1-4 is to be installed
                     Depends: libpython3-dev (= 3.5.1-3) but it is not going to be installed
                     Depends: python3.5-dev (&gt;= 3.5.1-2~) but it is not going to be installed
      E: Unable to correct problems, you have held broken packages.
  </code></pre>