Autodoc generates invalid xml

[nemani]

Describe the bug

When using autodoc along with python function signatures containing "params" with XML builder the generated xml is not valid.

We think the issue is due to the following commit: 30c594f

How to Reproduce

1. git clone https://github.com/nemani/sphinx-bug-report-example
2. Install sphinx
3. cd docs
4. make xml
5. xmllint --noout docs/build/xml/index.xml

Expected behavior

The generated XML should be valid and xml lint should not have any errorss

Your project

https://github.com/nemani/sphinx-bug-report-example

Screenshots

No response

OS

mac

Python version

3.7.5

Sphinx version

4.0.3

Sphinx extensions

sphinx.ext.autodoc

Extra tools

Additional context

[nemani]

This is being a huge blocker for me.
@tk0miya any suggested workarounds for this?

[nemani]

I have a suggested fix up as a PR.

[wvxvw]

The moment I thought to have finally found a solution to work around autodoc bugs... this appears to be also broken at the baseline. Lol. Please, please fix it... the amount of work I've invested already in trying to generate documentation and trying to work around broken parts is getting into the area where it would've been just easier to do it all from scratch.