Pip installation of demjson broken under setuptools>=58

[carlwilson]

Recent versions of setuptools cause the installation of demjson to fail with the following error:

Collecting demjson                                                                                                                                                                            
  Downloading demjson-2.2.4.tar.gz (131 kB)                                                                                                                                                   
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 131.5/131.5 kB 1.3 MB/s eta 0:00:00                                                                                                             
  Preparing metadata (setup.py) ... error                                                                                                                                                     
  error: subprocess-exited-with-error                                                                                                                                                         
                                                                                                                                                                                              
  × python setup.py egg_info did not run successfully.                                                                                                                                        
  │ exit code: 1                                                                                                                                                                              
  ╰─> [1 lines of output]                                                                                                                                                                     
      error in demjson setup command: use_2to3 is invalid.                                                                                                                                    
      [end of output]                                                                                                                                                                         
                                                                                                                                                                                              
  note: This error originates from a subprocess, and is likely not a problem with pip.                                                                                                        
error: metadata-generation-failed                                                                                                                                                             

I've bodged this in the new GitHub actions by forcing a downgrade of setup tools so: pip install "setuptools<58" for now but it's a sticking plaster.

[carlwilson]

This output from my desktop GitHub actions run looks pretty relevant:

DEPRECATION: demjson is being installed using the legacy 'setup.py install' method, because it does not have a 'pyproject.toml' and the 'wheel' package is not installed. pip 23.1 will en
force this behaviour change. A possible replacement is to enable the '--use-pep517' option. Discussion can be found at https://github.com/pypa/pip/issues/8559 

See here for issue discussion: pypa/pip#8559