[lldb] Print an actionable error message when sphinx_automodapi is not installed

[JDevlieghere]

Summary

Print an error message with instructions on how to install sphinx_automodapi.

[mib]

We should really add a requirements.txt file with all the dependencies.

[JDevlieghere]

In D158022#4590291, @mib wrote:

We should really add a requirements.txt file with all the dependencies.

I've long wanted to make this all automated, and have CMake install all the necessary dependencies. But that seems a bit intrusive without using something like a virtual environment, which would have to be project-wide and more work than I'm willing to put in. Regardless, that wouldn't actually help here, at least not on macOS if you installed sphinx with homebrew, because it packages its own version of Python (/opt/homebrew/Cellar/sphinx-doc/7.1.2/libexec/bin/python) and you have to install the sphinx_automodapi module with that. That's why I print sys.executable and really the motivation behind this patch.

[bulbazord]

From the discussion this sounds like a reasonable thing to do.

[DavidSpickett]

I was in this exact situation yesterday but luckily I had already used a virtualenv to fix some other Python problems so I knew how to fix it. Had it not been for that, seeing the exact Python path would have been very useful here, thanks for adding this message.

lldb/docs/conf.py

 
 autodoc_default_options = {
     "special-members": "__int__, __len__, __hex__, __oct__, __iter__",
 }
 
 # Unless we only generate the basic manpage we need the plugin for generating
 # the Python API documentation.
 if not building_man_page:
+    try:
+        import sphinx_automodapi.automodapi
+    except ModuleNotFoundError:
+        print(
+            f"install sphinx_automodapi with {sys.executable} -m pip install sphinx_automodapi"
+        )
     extensions.append("sphinx_automodapi.automodapi")
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ["_templates"]
 
 # The suffix of source filenames.
 source_suffix = {
     ".rst": "restructuredtext",