Use valid XHTML syntax

[pmoura]

The following lines:

sphinx_rtd_theme/sphinx_rtd_theme/layout.html

Lines 15 to 17 in 1d85625

	<meta charset="utf-8">
	{{ metatags }}
	<meta name="viewport" content="width=device-width, initial-scale=1.0">

should be:

<meta charset="utf-8" /> 
{{ metatags }} 
<meta name="viewport" content="width=device-width, initial-scale=1.0" /> 

[utzig]

Not really, <meta> tags are empty elements: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta

[pmoura]

Without these fixes we get invalid EPUB files due to invalid XHTML (not HTML!) files.

[pmoura]

P.S. Same fixes have already been applied to the themes bundled with Sphinx (in July 17): sphinx-doc/sphinx@267eeab

[pmoura]

In the just released Sphinx Release 3.2.0, the bug fix is listed as:

#7846: html theme: XML-invalid files were generated