3.0.0: sphinx warnings `reference target not found`

[kloczek]

On building my packages I'm using sphinx-build command with -n switch which shows warmings about missing references. These are not critical issues.
Here is the output with warnings:

+ /usr/bin/sphinx-build -n -T -b man docs/source build/sphinx/man
Running Sphinx v8.1.3
loading translations [en]... done
making output directory... done
WARNING: html_static_path entry '_static' does not exist
Converting `source_suffix = ['.rst', '.md']` to `source_suffix = {'.rst': 'restructuredtext', '.md': 'restructuredtext'}`.
building [mo]: targets for 0 po files that are out of date
writing output...
building [man]: all manpages
updating environment: [new config] 3 added, 0 changed, 0 removed
reading sources... [100%] index
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.parse:4: WARNING: Explicit markup ends without a blank line; unexpected unindent. [docutils]
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
copying assets...
copying assets: done
writing... python-ulid.3 {
 api
  changelog
} /home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_bytes:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_datetime:1: WARNING: py:class reference target not found: datetime.datetime [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_datetime:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_hex:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_int:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_str:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_timestamp:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_timestamp:1: WARNING: py:func reference target not found: time.time [ref.func]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_uuid:1: WARNING: py:class reference target not found: uuid.UUID [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_uuid:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.from_uuid:1: WARNING: py:class reference target not found: uuid.UUID [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.parse:1: WARNING: py:class reference target not found: ulid.U [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.to_uuid:1: WARNING: py:class reference target not found: uuid.UUID [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.to_uuid:1: WARNING: py:class reference target not found: uuid.UUID [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.to_uuid4:1: WARNING: py:class reference target not found: uuid.UUID [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.to_uuid4:1: WARNING: py:class reference target not found: uuid.UUID [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.to_uuid4:3: WARNING: py:class reference target not found: uuid.UUID [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/ulid/__init__.py:docstring of ulid.ULID.datetime:1: WARNING: py:class reference target not found: datetime.datetime [ref.class]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/CHANGELOG.rst:131: WARNING: py:attr reference target not found: __version__ [ref.attr]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/CHANGELOG.rst:156: WARNING: py:meth reference target not found: ULID.new [ref.meth]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/CHANGELOG.rst:172: WARNING: py:meth reference target not found: ULID.str [ref.meth]
/home/tkloczko/rpmbuild/BUILD/python-ulid-3.0.0/CHANGELOG.rst:172: WARNING: py:meth reference target not found: ULID.int [ref.meth]
done
build succeeded, 24 warnings.

You can peak on fixes that kind of issues in other projects
RDFLib/rdflib-sqlalchemy#95
RDFLib/rdflib#2036
click-contrib/sphinx-click@abc31069
frostming/unearth#14
jaraco/cssutils#21
latchset/jwcrypto#289
latchset/jwcrypto#289
pypa/distlib@98b9b89f
pywbem/pywbem#2895
sissaschool/elementpath@bf869d9e
sissaschool/xmlschema@42ea98f2
sqlalchemy/sqlalchemy@5e88e6e8