This is what I get:

Run xvfb-run make -C Doc/ PYTHON=../python SPHINXOPTS="-q -W --keep-going -j4" doctest suspicious html
make: Entering directory '/home/runner/work/cpython/cpython/Doc'
make[1]: Entering directory '/home/runner/work/cpython/cpython/Doc'
mkdir -p build
Building NEWS from Misc/NEWS.d with blurb
PATH=./venv/bin:$PATH sphinx-build -b doctest -d build/doctrees  -q -W --keep-going -j4 -W . build/doctest 
Warning: ../build/NEWS:111: WARNING: Inline emphasis start-string without end-string.
/home/runner/work/cpython/cpython/Lib/socket.py:775: ResourceWarning: unclosed <socket.socket fd=7, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('10.1.0.4', 39496), raddr=('116.202.254.214', 119)>
  self._sock = None
ResourceWarning: Enable tracemalloc to get the object allocation traceback
<doctest default[0]>:1: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
  import imp
<doctest default[2]>:1: DeprecationWarning: `formatargspec` is deprecated since Python 3.5. Use `signature` and the `Signature` object directly
  formatargspec(*getfullargspec(f))
Makefile:49: recipe for target 'build' failed
make[1]: *** [build] Error 1
make[1]: Leaving directory '/home/runner/work/cpython/cpython/Doc'
Testing of doctests in the sources finished, look at the results in build/doctest/output.txt
Makefile:127: recipe for target 'doctest' failed
make: *** [doctest] Error 1
make: Leaving directory '/home/runner/work/cpython/cpython/Doc'
Error: Process completed with exit code 2.