Python bindings broken on Windows

[timwoj]

This may be something specific to Visual Studio 2019 and above, or it may not be. As part of #214, we discovered that the python bindings aren't getting loaded correctly on Windows. It appears that the DLL isn't being autoloaded when import _broker is called from the __init__.py file for the broker module:

Traceback (most recent call last):
  File "C:\broker\build\python\broker\__init__.py", line 3, in <module>
    from . import _broker
ImportError: cannot import name '_broker' from partially initialized module 'broker' (most likely due to a circular import) (C:\broker\bui
ld\python\broker\__init__.py)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\broker\tests\python\communication.py", line 8, in <module>
    import broker
  File "C:\broker\build\python\broker\__init__.py", line 5, in <module>
    import _broker
ModuleNotFoundError: No module named '_broker'

This works correctly on macOS and Linux where it loads a shared object. There were some changes around DLL loading in Python 3.8, but I tested it on both 3.6 and 3.10 and it doesn't work on either of them.

[timwoj]

Note that building python on Windows is currently disabled for CI builds and should be re-enabled once this is fixed.

[Neverlord]

@timwoj I've seen that you've pushed some changes to the Broker bindings. Is this fixed?

[timwoj]

I don't believe so, but I can revert e7d9692 and check.

[timwoj]

No, still broken here: https://cirrus-ci.com/task/5149945408782336

[Neverlord]

After 5.0, we've wanted to revisit the need for Python bindings with WebSockets available (see #212). If we do end up deprecating (and later removing) the bindings, there's probably no point in fixing this.