At present, latest typted_ast does not support python-3.9a1 or later.
As a result, nightly python in Travis CI gets errored in nearly running.
This stops to use nightly python for testing temporarily.
refs: https://github.com/python/typed_ast/issues/129
Refs: #6890
The comma character is not TeX-escaped because it is frequent in general
text and escaping it would make the LaTeX output larger for only dealing
with the problem of the LaTeX-ligature of ,, into a single character.
And one there is problem with the commas in options to Verbatim from
PygmentsBridge.
The hyphen character is escaped (not in ids and URIs!) to
\sphinxhyphen{} for both Unicode and non-Unicode engines. This is needed
to work around hyperref transforming -- and --- from section titles into
EN DASH resp. EM DASH in PDF bookmarks.
https://github.com/latex3/hyperref/issues/112
Note to expert LaTeX users: if Sphinx latex user with xelatex has
- turned off Smart Quotes for some reason,
- but does want TeX ligatures and thus overrode Sphinx
latex_elements['fontenc'] default (since #6888) to this effect,
then this should be added to LaTeX preamble:
\def\sphinxhyphen#1{-}% (\protected is now not needed)
\let\sphinxhyphenforbookmarks\sphinxhyphen
Closes: #6886
It is difficult to understand why fontspec _by default_ turns straight
double quotes " into ” i.e. right curly ones, calling this "TeX
ligature", but that's life and fortunately fontspec also provides a way
to turn this off. With this workaround also a straight ' in LaTeX file,
(i.e. a straight ' in source and smartquotes = False was used) will not
become a curly quote and this is an advantage compared to the pdflatex
situation.
We suppress TeX Ligatures also for \ttfamily (used in code-blocks) but
that appears to be already the case with fontspec although user manual
does not seem explicit (and no list of what exactly the TeX Ligatures
are is to be found in fontspec user documentation, one has to go into
its source code). (the fact that Pygmentize escapes the " to \char`\"
TeX mark-up would not by itself prevent the transformation into a curly
double quote, it is because fontspec does not apply this transform to
monospace typeface that it did not show).
