Install apt-install repositories by apt.txt file like mybinder

[tkoyama010]

Details

• Read the Docs project URL: https://github.com/tkoyama010/pyvista-doc-translations
• Build URL (if applicable): https://readthedocs.org/projects/pyvista-doc/builds/11602772/
• Read the Docs username (if applicable): tkoyama010

Expected Result

• A description of what you wanted to happen*

I need to install libgl1-mesa-dev xvfb ffmpeg by apt command to compile sphinx document.
I think I am happy if I can install it by apt.txt file like mybinder.

Actual Result

A description of what actually happened
The following error happend. Because I cannot install packages of apt.
https://readthedocs.org/projects/pyvista-doc/builds/11602772/

Running Sphinx v1.8.5
loading translations [en]... done
making output directory...
generating gallery...
generating gallery for examples/00-load... [  7%] create-geometric-objects.py
2020-08-05 17:46:58.219 (   5.024s) [        BF82F080]vtkXOpenGLRenderWindow.:449    ERR| vtkXOpenGLRenderWindow (0x55bd4870d440): bad X server connection. DISPLAY=
Fatal Python error: Aborted

Current thread 0x00007fd4bf82f080 (most recent call first):
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/checkouts/latest/pyvista/pyvista/plotting/plotting.py", line 4060 in show
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/checkouts/latest/pyvista/examples/00-load/create-geometric-objects.py", line 53 in <module>
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx_gallery/gen_rst.py", line 466 in __call__
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx_gallery/gen_gallery.py", line 159 in call_memory
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx_gallery/gen_rst.py", line 548 in execute_code_block
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx_gallery/gen_rst.py", line 717 in execute_script
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx_gallery/gen_rst.py", line 797 in generate_file_rst
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx_gallery/gen_rst.py", line 364 in generate_dir_rst
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx_gallery/gen_gallery.py", line 381 in generate_gallery_rst
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx/events.py", line 80 in emit
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx/application.py", line 510 in emit
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx/application.py", line 325 in _init_builder
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx/application.py", line 263 in __init__
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx/cmd/build.py", line 303 in build_main
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/lib/python3.7/site-packages/sphinx/cmd/build.py", line 319 in main
  File "/home/docs/checkouts/readthedocs.org/user_builds/pyvista-doc/envs/latest/bin/sphinx-build", line 8 in <module>
Aborted (core dumped)

[stsewd]

Duplicated of #6662