title: pip install -e option requires 1 argument
body: <p>I am following Flask's official tutorial, and get an error in the <a href="http://flask.pocoo.org/docs/1.0/tutorial/install/#describe-the-project" rel="nofollow noreferrer">Making the project installable</a> step. When I run <code>pip install -e</code>, I get the following error:</p>
  
  <pre><code>Usage:   
    pip install [options] &lt;requirement specifier&gt; [package-index-options] ...
    pip install [options] -r &lt;requirements file&gt; [package-index-options] ...
    pip install [options] [-e] &lt;vcs project url&gt; ...
    pip install [options] [-e] &lt;local project path&gt; ...
    pip install [options] &lt;archive url/path&gt; ...
  
  -e option requires 1 argument
  </code></pre>