Before every sphinx update a copr repo is set to test the dependant packages.

With Sphinx 3.5.1, python-sphinxcontrib-bibtex is failing to build from source with:

_______________________________ test_latex_refs ________________________________

app = <SphinxTestApp buildername='latex'>
warning = <_io.StringIO object at 0x7fbc7ac1b9d0>

    @pytest.mark.sphinx('latex', testroot='latex_refs')
    def test_latex_refs(app, warning):
        app.build()
        assert not warning.getvalue()
        output = (app.outdir / "test.tex").read_text()
        assert len(common.latex_citations().findall(output)) == 1
        assert len(common.latex_citation_refs().findall(output)) == 1
        match = common.latex_citations().search(output)
        match_ref = common.latex_citation_refs().search(output)
        assert match.group('label') == 'Huy57'
        assert match.group('docname') == 'index'
>       assert "De ratiociniis in ludo aleæ." in match.group('text')
E       AssertionError: assert 'De ratiociniis in ludo aleæ.' in '\\sphinxAtStartPar'
E        +  where '\\sphinxAtStartPar' = <built-in method group of re.Match object at 0x7fbc7c753920>('text')
E        +    where <built-in method group of re.Match object at 0x7fbc7c753920> = <re.Match object; span=(2288, 2333), match='\\bibitem[Huy57]{index:id3}\n\\sphinxAtStartPar\n>.group

test/test_latex.py:16: AssertionError
--------------------------- Captured stdout teardown ---------------------------
# testroot: root
# builder: latex
# srcdir: /tmp/pytest-of-mockbuild/pytest-1/latex_refs
# outdir: /tmp/pytest-of-mockbuild/pytest-1/latex_refs/_build/latex
# status: 
Running Sphinx v3.5.1
checking for /tmp/pytest-of-mockbuild/pytest-1/latex_refs/test.bib in bibtex cache... not found
parsing bibtex file /tmp/pytest-of-mockbuild/pytest-1/latex_refs/test.bib... parsed 1 entries
building [mo]: targets for 0 po files that are out of date
building [latex]: all documents
updating environment: [new config] 1 added, 0 changed, 0 removed
reading sources... [100%] index                                                
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
processing test.tex... index 
resolving references...
done
writing... done
copying TeX support files... copying TeX support files...
done
build succeeded.

The LaTeX files are in ../../../../tmp/pytest-of-mockbuild/pytest-1/latex_refs/_build/latex.
Run 'make' in that directory to run these through (pdf)latex
(use `make latexpdf' here to do that automatically).

# warning: 

=========================== short test summary info ============================
FAILED test/test_latex.py::test_latex_refs - AssertionError: assert 'De ratio...
======================== 1 failed, 54 passed in 10.06s =========================


Link to logs: https://copr.fedorainfracloud.org/coprs/cstratak/sphinx_3_5/build/1970724/