Class variable name cross referencing

[heavelock]

Describe the bug
Names of class variables that are described with :ivar are getting cross-referenced. I would rather expect that this would not be crossreferenced, as the names of parameters (:param:) in methods are not.

Here is a screenshot:

Notice here names of variables time and phase. Both are links. The former one is linked to python's time module, the latter is linked to some not relevant part of our code.

Code that defines that page is here:
https://github.com/obspy/obspy/blob/master/obspy/taup/helper_classes.py

I tried to use :samp: directive but it breaks rendering. obspy/obspy#2662 (comment)

To Reproduce
Steps to reproduce the behavior:

$ apt-get install apt-get install -yqq build-essential gcc libproj-dev proj-data proj-bin libgeos-dev
$ python -m pip install numpy
$ python -m pip install shapely --no-binary shapely
$ git clone git@github.com:obspy/obspy.git
$ cd obspy
$ git switch sphinx3
$ pip install .
$ cd misc/docs
$ python -m pip install -r requirements.txt
$ make html
$ # open build/html/packages/autogen/obspy.taup.helper_classes.Arrival.html and see the class vars of Arrival

Expected behavior
Names of class variables should not be links. Exactly as names of method parameters are not.

Your project
https://github.com/obspy/obspy

Environment info

• OS: Linux
• Python version: 3.8.7
• Sphinx version: 3.4.3
• Sphinx extensions:

    'sphinx.ext.intersphinx',
    'sphinx.ext.doctest',
    'sphinx.ext.autodoc',
    'sphinx.ext.viewcode',
    'sphinx.ext.mathjax',
    'sphinx.ext.autosummary',
    'sphinx.ext.coverage',
    'sphinx.ext.duration',
    'sphinx.ext.todo',
    'm2r2',
    # theme
    'sphinx_rtd_theme',
    # custom extensions
    'plot_directive',
    'credits',
    'citations',

• Extra tools: [e.g. Browser, tex or something else]

Additional context
Add any other context about the problem here.

• [e.g. URL or Ticket]

[tk0miya]

This will be fixed in 4.0.0 release (refs: #8638).
Thanks,