When 'pointsize' is not 10pt Japanese 'manual' badly renders in PDF

[jfbu]

Subject: when 'pointsize' is used, the paper dimensions get wrong with 'manual' class.

Test file (I picked up some random Japanese text...)

Welcome to FOO's documentation!
===============================

.. toctree::
   :maxdepth: 2


CHAPTER 1
---------

A

TeXが未定義の命令名を発見しました．おそらく入力の誤りでしょう．もしこ
のエラーがLaTeX命令の処理中に生じた場合は，その命令は間違った位置に置か
れています．例えば，リスト環境の中でないのに\item命令が使われた場合など
です．また，``\documentclass`` 命令がない場合にもこのエラーが生じます．


CHAPTER 2
---------

B

with

latex_elements = {
    # The paper size ('letterpaper' or 'a4paper').
    #
    # 'papersize': 'letterpaper',

    # The font size ('10pt', '11pt' or '12pt').
    #
    'pointsize': '21pt',
}

and 'manual' docclass and 'ja' language.

Problem

• The output is bad:

The page dimensions are much bigger than the expected letterpaper.

Explanation of the problem

This is due to incompatibility of jsbook document class with geometry package if no special measures are taken.

Expected result

Something like:

In this screen shot, Adobe Reader said page dimensions are those of US letter, as expected.

Environment info

• Sphinx version: 1.5.2
• TeX version: TeXLive 2016, more or less up-to-date.

This will be fixed at #3387

Related: #3356

[jfbu]

(the issue was illustrated with 21pt for drama, but it is also there for 12pt)

[jfbu]

fixed at 09324bd and parent commits (#3387)