Sphinx 2.? generates different html than 1.8 such that the display of  
Help ==> IDLE Help has extra blank lines. Among possibly other things, the contents of <li>...</li> is wrapped in <p>...</p> and blank lines appear between the bullet and text.
 
<ul class="simple">
-<li>coded in 100% pure Python, using the <a class="reference internal" href="tkinter.html#module-tkinter" title="tkinter: Interface to Tcl/Tk for graphical user interfaces"><code class="xref py py-mod docutils literal notranslate"><span class="pre">tkinter</span></code></a> GUI toolkit</li>
-<li>cross-platform: works mostly the same on Windows, Unix, and macOS</li>
...
+<li><p>coded in 100% pure Python, using the <a class="reference internal" href="tkinter.html#module-tkinter" title="tkinter: Interface to Tcl/Tk for graphical user interfaces"><code class="xref py py-mod docutils literal notranslate"><span class="pre">tkinter</span></code></a> GUI toolkit</p></li>
+<li><p>cross-platform: works mostly the same on Windows, Unix, and macOS</p></li>
...
 </ul>

A similar issue afflicts the menu, with blank lines between the menu item and the explanation.

The html original 3x/Doc/build/html/library/idle.html#index-0 looks normal in Firefox.  The html parser class in help.py needs to ignore <p> within <li>.  It should specify which version of Sphinx it is compatible with.

Do any of you have any idea what the html change might be about?  Is there something wrong with idle.rst?