title: How to fix the error `found no layout file for "HTML" for "page"` in Hugo CMS?
body: <p>I recently imported content from my WordPress page into Hugo. When I run <code>hugo serve</code> I get following error messages:</p>
  
  <pre><code>WARN 2020/02/17 20:51:06 found no layout file for "HTML" for "page": You should create a template file which matches Hugo Layouts Lookup Rules for this combination.
  </code></pre>
  
  <p>The page in question starts like this:</p>
  
  <pre><code>---
  linktitle: "The Title of the Post"
  title: "The Title of the Post"
  author: "Franz Drollig"
  type: post
  date: 2020-01-09T14:41:55+00:00
  url: /the-title-of-post/
  categories:
    - Uncategorized
  weight: 10
  
  ---
  
  
  This is the content of the post. This is the second sentence of the post. 
  </code></pre>
  
  <p>It is located in <code>mysite/content/posts/YYYY-MM-DD-title.md</code>.</p>
  
  <p>The <code>layouts</code> directory is empty. However, the <code>themes</code> directory contains the <a href="https://themes.gohugo.io/hugo-book/" rel="noreferrer">book</a> theme. This theme is also configured in the <code>config.toml</code>.</p>
  
  <p>Another post, starting like shown below, is rendered correctly.</p>
  
  <pre><code>---
  author: "Michael Henderson"
  date: 2014-09-28
  linktitle: Creating a New Theme
  menu:
    main:
      parent: tutorials
  next: /tutorials/github-pages-blog
  prev: /tutorials/automated-deployments
  title: Creating a New Theme
  weight: 10
  ---
  
  
  ## Introduction
  </code></pre>
  
  <p>Why is my post not rendered properly? How can I fix it?</p>