title: When installing packages with Yarn, what does "incorrect peer dependency" mean?
body: <p>I've just cloned <a href="https://github.com/davezuko/react-redux-starter-kit/" rel="noreferrer">a repo</a>, which recommends the use of <a href="https://yarnpkg.com" rel="noreferrer">Yarn</a> to install dependencies. When I run <code>yarn install</code>, it seems to be okay, but it provides this warning:</p>
  <pre><code>yarn install v0.20.3
  [1/4]   Resolving packages...
  [2/4]   Fetching packages...
  [3/4]   Linking dependencies...
  warning &quot;sass-loader@4.0.2&quot; has incorrect peer dependency &quot;node-sass@^3.4.2&quot;.
  [4/4]   Building fresh packages...
  ✨  Done in 77.59s.
  </code></pre>
  <p>I've looked online to find out exactly what &quot;has incorrect peer dependency&quot; means. But all I can find are reported issues on other repositories or questions about how to fix the problem.</p>
  <p>Can someone explain what this means and why it is only a warning, and not an error?</p>
  <p>Also, is it something that I should try to address or report to the community behind the repo I have just cloned?</p>