Improve error message for missing packages when installed via git URL in requirements.txt

[hmedina]

Describe the bug

I have a document that specifies in its requirements.txt file a git+https link to a package; this gets installed under src/. If I remove that folder (e.g. to install the package in "editable form" elsewhere), a ModuleNotFoundError error appears, however it does not specify what module is missing. I'm reporting this as "Please also report this if it was a user error, so that a better error message can be provided next time."

How to Reproduce

Assuming the requirements.txt file contains something like

pygments >= 2.7.1, < 3
Pygments_Kappa_plugin @ git+https://github.com/hmedina/Pygments_Kappa_plugin.git

The package Pygments_Kappa_plugin will get installed under src/Pygments_Kappa_plugin. If I delete that folder, make clean & make html, I get:

$ make html
Running Sphinx v8.2.3
loading translations [en]... done
making output directory... done
checking bibtex cache... out of date
parsing bibtex file /home/hmedina/project/bibliography.bib... parsed 70 entries


Versions
========

* Platform:         linux; (Linux-5.15.167.4-microsoft-standard-WSL2-x86_64-with-glibc2.39)
* Python version:   3.13.2 (CPython)
* Sphinx version:   8.2.3
* Docutils version: 0.21.2
* Jinja2 version:   3.1.6
* Pygments version: 2.19.1

Last Messages
=============

None.

Loaded Extensions
=================

None.

Traceback
=========

      File "<frozen importlib._bootstrap>", line 1324, in _find_and_load_unlocked
    ModuleNotFoundError: No module named 'core'


The full traceback has been saved in:
/tmp/sphinx-err-clglaqti.log

To report this error to the developers, please open an issue at <https://github.com/sphinx-doc/sphinx/issues/>. Thanks!
Please also report this if it was a user error, so that a better error message can be provided next time.
make: *** [Makefile:20: html] Error 2

A better error message would mention that a package, Pygments_Kappa_plugin, is now missing, instead of only mentioning core.

Environment Information

Platform:              linux; (Linux-5.15.167.4-microsoft-standard-WSL2-x86_64-with-glibc2.39)
Python version:        3.13.2 (main, Feb 12 2025, 04:07:04) [GCC 13.3.0])
Python implementation: CPython
Sphinx version:        8.2.3
Docutils version:      0.21.2
Jinja2 version:        3.1.6
Pygments version:      2.19.1

Sphinx extensions

Additional context

No response

[Tor-Erik-Aasestad]

Hello, im trying to reproduce this issue but i can not figure out how you are getting this error.

after adding the following none-existent extention to my conf.py

extensions = ["missing_thing"]

Traceback
=========

      File "/home/tor_erik/code/sphinx/sphinx/registry.py", line 546, in load_extension
        raise ExtensionError(
    sphinx.errors.ExtensionError: Could not import extension missing_thing (exception: No module named 'missing_thing')

Then i tried using another extentsion trick

extensions = ["sphinx.ext.autodoc"]

which gave the following warning

WARNING: autodoc: failed to import function 'fo' from module 'missing'; the following exception was raised:
['Traceback (most recent call last):\n', '  File "/home/tor_erik/code/sphinx/sphinx/ext/autodoc/importer.py", line 270, in import_object\n    module = import_module(modname, try_reload=True)\n             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n', '  File "/home/tor_erik/code/sphinx/sphinx/ext/autodoc/importer.py", line 173, in import_module\n    raise ModuleNotFoundError(msg, name=modname)  # NoQA: TRY301\n    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n', "ModuleNotFoundError: No module named 'missing'\n"] [autodoc.import_object]

using sphinx-build 8.3.0+/7b4164a

Not sure if I'm troubleshooting the correct way but seems to me like this has been adressed.

[AA-Turner]

Thanks @Tor-Erik-Aasestad for the detailed investigation, I'll close this issue in the meantime.

A