regression: builtin latex rendering doesn't find the right mathematical fonts

[boffi]

Matplotlib 1.5.1, installed by conda
Python 3.5.1 |Continuum Analytics, Inc.| (default, Jun 15 2016, 15:32:45)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux

I have this regression, starting from today the matplotlib builtin latex rendering doesn't find the right mathematical fonts.
I have to say that (earlier) today a conda update --all had installed a new version of fontconfig and on the whole it smells of a packaging problem... anyway...

My code

>>> import matplotlib.pyplot as plt
>>> plt.xlabel('$x_1$')
<matplotlib.text.Text object at 0x7fcc8c846c50>
>>> plt.plot(range(3))
[<matplotlib.lines.Line2D object at 0x7fcc7bd69198>]
>>> plt.show()

my output, please look at the index of x

[boffi]

There is something strange with the font cache,

boffi@debian:~$ find | grep fontList.cache
boffi@debian:~$ python
Python 3.5.1 |Continuum Analytics, Inc.| (default, Jun 15 2016, 15:32:45) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from matplotlib.font_manager import FontManager
>>> FontManager()
/home/boffi/src/miniconda3/lib/python3.5/site-packages/matplotlib/font_manager.py:274: UserWarning: Matplotlib is building the font cache using fc-list. This may take a moment.
  warnings.warn('Matplotlib is building the font cache using fc-list. This may take a moment.')
/home/boffi/src/miniconda3/lib/python3.5/site-packages/matplotlib/font_manager.py:274: UserWarning: Matplotlib is building the font cache using fc-list. This may take a moment.
  warnings.warn('Matplotlib is building the font cache using fc-list. This may take a moment.')
<matplotlib.font_manager.FontManager object at 0x7f22e57b8a58>
>>> 
boffi@debian:~$ find | grep fontList.cache
boffi@debian:~$ 

1. at the beginning, I have no fontList.cache (it used to be in ~/.cache/matplotlib/fontList.cache`)
2. the font manager tells me (twice, once for TTF and once for AFM, isn't it?) that it's building the font cache and doesn't signal any error
3. at the end, I still cannot see any fontList.cache file...

[QuLogic]

It is fontList.py3k.cache for Python 3.

[tacaswell]

What is in your rcparams?

I can not reproduce this in a fresh environment (conda create -n mpl151 python=3.5 matplotlib)

(and yes I know 'works for me' is the worst developer response ever)

[boffi]

The fontList cache file is in its place, as suggested by QuLogic, under its new name.
Tacaswell asks for my rcParams, here it is
rcParams.txt
and shows that in a new environment the subscript is rendered using the correct font,
so I too installed a new environment and yet I have not the correct font.

Is it possible that the new environment is built using the cached components of the installation?.. My problems started following a conda update --all.

PS: as far as I can recollect, the only change in rcParams I made concerns placing Ms Comic atop of the fantasy fonts' list.

[boffi]

Update

1. I created a new user on my system, had they install a fresh miniconda3 environment, install matplotlib in it, run my example and everything latex rendering showed up fine... So it's me after all...
2. I removed and reinstalled miniconda3, installed matplotlib and ran my example — the font cache was not remade, because I let in place all the configuration stuff in hidden files and directories — and voilà the subscript is correct...

I'm sorry that, as I've just realized, I've destroyed the possibility of replying and eventually fixing my particular regression.

[tacaswell]

This may be related to #6617

[tacaswell]

Closing in favor of #6976 which has much more detail and reproduction instructions.