Windows + Python 3.8 or later: ImportError: DLL load failed

[jwilk]

I've failed to make python-djvulibre work with Python 3.8 or any later version.
The tests fail with:

======================================================================
ERROR: test_const (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_const
Traceback (most recent call last):
  File "C:\Python38\lib\unittest\loader.py", line 436, in _find_test_path
    module = self._get_module_from_name(name)
  File "C:\Python38\lib\unittest\loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "C:\projects\python-djvulibre\tests\test_const.py", line 16, in <module>
    from djvu.const import (
  File "C:\projects\python-djvulibre\djvu\const.py", line 18, in <module>
    import djvu.sexpr
ImportError: DLL load failed while importing sexpr: The specified module could not be found.

Full build logs:

• Python 3.8 + DjVuLibre 3.5.28:
  https://ci.appveyor.com/project/jwilk/python-djvulibre/build/B14/job/2l3hxaqrr2l86ndx

• Python 3.9 + DjvuLibre 3.5.28:
  https://ci.appveyor.com/project/jwilk/python-djvulibre/build/B14/job/uxp406j47lwwl6lm

• Python 3.10 + DjVuLibre 3.5.28:
  https://ci.appveyor.com/project/jwilk/python-djvulibre/build/B14/job/nyh6gu2vxcvld8hv