#4068: Update linkcheck docs to use requests

doc/builders.rst

@@ -423,8 +423,8 @@ instructions.
 .. class:: CheckExternalLinksBuilder
 
    This builder scans all documents for external links, tries to open them with
-   :mod:`urllib2`, and writes an overview which ones are broken and redirected
-   to standard output and to :file:`output.txt` in the output directory.
+   ``requests``, and writes an overview which ones are broken and redirected to
+   standard output and to :file:`output.txt` in the output directory.
 
    .. autoattribute:: name
 
@@ -432,6 +432,10 @@ instructions.
 
    .. autoattribute:: supported_image_types
 
+   .. versionchanged:: 1.5
+
+      Since Sphinx-1.5, the linkcheck builder comes to use requests module.
+
 .. module:: sphinx.builders.xml
 .. class:: XMLBuilder