Documentation builds requires Latex for matplotlib plots

Since we are not going to have Latex installed in our CI machines anymore, this is failing.

See: https://gitlab.idiap.ch/bob/bob.ip.gabor/-/jobs/91810

+ sphinx-build -W /local/builds/bob/bob.ip.gabor/conda/../doc /local/builds/bob/bob.ip.gabor/conda/../sphinx
Running Sphinx v1.6.3
making output directory...
Adding intersphinx source for `python': https://docs.python.org/2.7/
Adding intersphinx source for `numpy': https://docs.scipy.org/doc/numpy-1.12.0/
Adding intersphinx source for `matplotlib': http://matplotlib.org/
Adding intersphinx source for `setuptools': https://setuptools.readthedocs.io/en/latest/
Found documentation for bob.extension on http://www.idiap.ch/software/bob/docs/bob/bob.extension/master/; adding intersphinx source
Found documentation for bob.blitz on http://www.idiap.ch/software/bob/docs/bob/bob.blitz/master/; adding intersphinx source
Found documentation for bob.core on http://www.idiap.ch/software/bob/docs/bob/bob.core/master/; adding intersphinx source
Found documentation for bob.io.base on http://www.idiap.ch/software/bob/docs/bob/bob.io.base/master/; adding intersphinx source
Found documentation for bob.sp on http://www.idiap.ch/software/bob/docs/bob/bob.sp/master/; adding intersphinx source
loading pickled environment... not yet created
[autosummary] generating autosummary for: c_cpp_api.rst, guide.rst, index.rst, py_api.rst
loading intersphinx inventory from http://www.idiap.ch/software/bob/docs/bob/bob.sp/master/objects.inv...
loading intersphinx inventory from https://docs.python.org/2.7/objects.inv...
loading intersphinx inventory from http://matplotlib.org/objects.inv...
loading intersphinx inventory from http://www.idiap.ch/software/bob/docs/bob/bob.core/master/objects.inv...
loading intersphinx inventory from http://www.idiap.ch/software/bob/docs/bob/bob.extension/master/objects.inv...
loading intersphinx inventory from https://setuptools.readthedocs.io/en/latest/objects.inv...
loading intersphinx inventory from http://www.idiap.ch/software/bob/docs/bob/bob.blitz/master/objects.inv...
loading intersphinx inventory from http://www.idiap.ch/software/bob/docs/bob/bob.io.base/master/objects.inv...
loading intersphinx inventory from https://docs.scipy.org/doc/numpy-1.12.0/objects.inv...
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 4 source files that are out of date
updating environment: 4 added, 0 changed, 0 removed
reading sources... [ 25%] c_cpp_api
reading sources... [ 50%] guide
sh: latex: command not found
reading sources... [ 75%] index
reading sources... [100%] py_api


Warning, treated as error:
/local/builds/bob/bob.ip.gabor/doc/guide.rst:102: (WARNING/2) Exception occurred in plotting transform
 from /local/builds/bob/bob.ip.gabor/doc/plot/transform.py:
Traceback (most recent call last):
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/sphinxext/plot_directive.py", line 651, in render_figures
    figman.canvas.figure.savefig(img.filename(format), dpi=dpi)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/figure.py", line 1573, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/backend_bases.py", line 2252, in print_figure
    **kwargs)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 545, in print_png
    FigureCanvasAgg.draw(self)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 464, in draw
    self.figure.draw(self.renderer)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/figure.py", line 1144, in draw
    renderer, self, dsu, self.suppressComposite)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/image.py", line 139, in _draw_list_compositing_images
    a.draw(renderer)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/axes/_base.py", line 2426, in draw
    mimage._draw_list_compositing_images(renderer, self, dsu)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/image.py", line 139, in _draw_list_compositing_images
    a.draw(renderer)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/axis.py", line 1138, in draw
    renderer)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/axis.py", line 1078, in _get_tick_bboxes
    extent = tick.label1.get_window_extent(renderer)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/text.py", line 967, in get_window_extent
    bbox, info, descent = self._get_layout(self._renderer)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/text.py", line 353, in _get_layout
    ismath=False)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 230, in get_text_width_height_descent
    renderer=self)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/texmanager.py", line 676, in get_text_width_height_descent
    dvifile = self.make_dvi(tex, fontsize)
  File "/local/builds/bob/bob.ip.gabor/conda-env/bob.ip.gabor_1506366718035/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placeho/lib/python2.7/site-packages/matplotlib/texmanager.py", line 423, in make_dvi
    report))
RuntimeError: LaTeX was not able to process the following string:
'lp'
Here is the full report generated by LaTeX: 

Blocks bob.admin#35 (closed)