Blank pages of second language

[akram1]

I build using make html LANGUAGES=en,ar CURRENT_LANG=en. I noticed that I have to delete the builds and do it from scratch. It did build with two languages and language dropdown is active. However, if I select the second language, it comes blank page (ERR_FILE_NOT_FOUND). So ar option gives blank page. I did a new built it with LANGUAGES=en,ar CURRENT_LANG=ar. Arabic is good but English is blank page.

Beside this problem, I suggest the following:

1-
I think the line make html LANGUAGES=.... CURRENT_LANG=.... should be mentioned in the documentation. MakeFile does not mention that.

modify the readme file like bellow:

Instructions

In a terminal, navigate to the root directory of the documentation and build it make. This produces English version.
make help
html to build the documentation to HTML
fast to build the documentation to HTML with shallow menu (faster)
clean to delete the build files
test to run the guidelines tests
3- You can use of these 4 options to build. make without option is defaulted to html.
To build multi languagal make LANGUAGES=lang1,lang2,...., CURRENT_LANG=lang1 where lang1,2.. are language en,es,ar....
Check directory ./locale, to see available languages. Some languages are not fully translated, so feel free to modify any translations.
To rebuild, you need to delete the first build
Additional commands are available with make help.
Open the file documentation/_build/html/index.html in your web browser.7. See this guide for more detailed instructions.

2-
Upgrade the Python package requirements. They are outdated packages.

This issue is related to #14177