EVE Asset Converter failing

[durian]

I'm trying to use the EVE Asset Converter to convert some png file to L4. I'm running version 2.1.0-rc2.

Here is an example from the log:
----------------------------------------------------------------------
C:/EAB/Input/diving_16.png conversion is in progress...
Conversion failed!
EXCEPTION IN (img_cvt.py, LINE 942 ""): [Errno 13] Permission denied: 'output.txt'

Traceback (most recent call last):
  File "img_cvt.py", line 942, in image_convert
  File "img_cvt.py", line 799, in run
PermissionError: [Errno 13] Permission denied: 'output.txt'


It's not showing me the full path to output.txt, so I don't know why it can't create the file. A folder called SampleApp is created in the output folder and it contains a ReadMe.txt and a few subfolders, but that's it. I can't find anything that looks like it might be the output from my converted image.

I can't locate img_cvt.py in EAB executable folder either, so I'm not able to dig into this any further on my own.

On a related note, if the asset builder is written in Python, having the source would be very helpful. Then I could run it directly under MacOS. A command line conversion utility would be especially handy.