pip install succeeds, ImportError on import


Trying to work out some issues importing fiona.

Python 3.8.2
GDAL: http://download.gisinternals.com/sdk/downloads/release-1911-x64-gdal-3-0-4-mapserver-7-4-3.zip and associated libs
Everything installed via pip
Doing the `add_ddl_directory` call (already a pending PR for python 3.8) manually gets past the failure to find the module.
Now it fails to find a procedure, and I'm at a complete loss for how to hunt down the issue further.
Dependency walker run against `ogrext.cp38-win_amd64.pyd` shows issues, but I'm at a loss for how to solve them.

Python 3.8.2 (tags/v3.8.2:7b3ab59, Feb 25 2020, 23:03:10) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.add_dll_directory('c:\program files\gdal')
<AddedDllDirectory('c:\\program files\\gdal')>
>>> import fiona
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\gavin\covid_env\lib\site-packages\fiona\__init__.py", line 84, in <module>
    from fiona.collection import BytesCollection, Collection
  File "C:\Users\gavin\covid_env\lib\site-packages\fiona\collection.py", line 9, in <module>
    from fiona.ogrext import Iterator, ItemsIterator, KeysIterator
ImportError: DLL load failed while importing ogrext: The specified procedure could not be found.

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