Python 3.13: chunk removed

[einstein95]

Bug report

Problem
Running pcbasic with Python 3.13 gives

  File "/lib/python3.13/site-packages/pcbasic/basic/devices/cassette.py", line 14, in <module>
    from chunk import Chunk
ModuleNotFoundError: No module named 'chunk'

The 3.13 changelog and PEP-594 give more rationale for the removal.

It may be possible to rewrite cassette.py to use the wave module instead.

[robhagemans]

Thanks for flagging - easiest is probably to vendor in the old chunk module as it is small, pure Python and basically does precisely what we need. I think that's going to be for a 2.1 branch though, at this point the current 2.0 branch should be considered Python 2.7 - 3.12 only (metadata probably needs updating).

The 2.1 branch will target 3.9+, allowing a large amount of compatibility code to be dropped.