Blockcrafter-export fails with an error with Python

[edit] Cleaned this up as it was kind of a mess!

I got the 12 pixel texture size working in Mapcrafter with Minecraft 1.16.2, but the Mapcrafter output is way too big (~13GB) at so needed a smaller texture size which brought me to Blockcrafter from the other Issue I had posted in mapcrafter/mapcrafter#374.

I got Python working and installed the Blockcrafter package, but attempting the blockcrafter-export command fails with an error below.

D:\Mapcrafter\blockcrafter>pip3 install .
Processing d:\mapcrafter\blockcrafter
Requirement already satisfied: numpy in c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages (from blockcrafter==1.0) (1.19.1)
Requirement already satisfied: vispy in c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages (from blockcrafter==1.0) (0.6.4)
Requirement already satisfied: Pillow in c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages (from blockcrafter==1.0) (7.2.0)
Requirement already satisfied: freetype-py in c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages (from vispy->blockcrafter==1.0) (2.2.0)
Building wheels for collected packages: blockcrafter
  Building wheel for blockcrafter (setup.py) ... done
  Created wheel for blockcrafter: filename=blockcrafter-1.0-py3-none-any.whl size=103954 sha256=58f71d13b12468aaad8dc9148b5323e09d6b7bae20ea64cd1c9f9698d9c8ce6b
  Stored in directory: C:\Users\pweat\AppData\Local\Temp\pip-ephem-wheel-cache-hzaath6w\wheels\f9\eb\da\82a95935dbf4cb931bdf33e91866dd63328f19e60e7febeb56
Successfully built blockcrafter
Installing collected packages: blockcrafter
  Attempting uninstall: blockcrafter
    Found existing installation: blockcrafter 1.0
    Uninstalling blockcrafter-1.0:
      Successfully uninstalled blockcrafter-1.0
Successfully installed blockcrafter-1.0

D:\Mapcrafter\blockcrafter>
D:\Mapcrafter\blockcrafter>blockcrafter-export -a 1.16.2.jar -o blocks -v isometric -t 8 -r 0
WARNING: Traceback (most recent call last):
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Users\pweat\AppData\Local\Programs\Python\Python38\Scripts\blockcrafter-export.exe\__main__.py", line 7, in <module>
    sys.exit(main())
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\blockcrafter\export.py", line 216, in main
    c = Canvas(args)
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\blockcrafter\export.py", line 57, in __init__
    self.show()
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\app\canvas.py", line 429, in show
    self._backend._vispy_set_visible(visible)
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\app\backends\_qt.py", line 412, in _vispy_set_visible
    self.showNormal()
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\app\backends\_qt.py", line 508, in event
    out = super(QtBaseCanvasBackend, self).event(ev)
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\app\backends\_qt.py", line 508, in event
    out = super(QtBaseCanvasBackend, self).event(ev)
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\app\backends\_qt.py", line 825, in paintGL
    self._vispy_canvas.events.draw(region=None)
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\util\event.py", line 455, in __call__
    self._invoke_callback(cb, event)
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\util\event.py", line 473, in _invoke_callback
    _handle_exception(self.ignore_callback_errors,
  << caught exception here: >>
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\vispy\util\event.py", line 471, in _invoke_callback
    cb(event)
  File "c:\users\pweat\appdata\local\programs\python\python38\lib\site-packages\blockcrafter\export.py", line 188, in on_draw
    blockstates = self.assets.blockstates
AttributeError: 'Canvas' object has no attribute 'assets'
ERROR: Invoking <bound method Canvas.on_draw of <Canvas (PyQt5) at 0x1c5ff8f0850>> for DrawEvent
WARNING: QOpenGLContext::swapBuffers() called with null argument

Start with blockcrafter/export.py, especially Canvas.init around line 57 and Canvas.on_draw around line 188. Reproduce the failure using the posted blockcrafter-export command and inspect how the Canvas instance obtains assets. Done means the command no longer raises the reported AttributeError during drawing.