Fedora 39 failure due to Python 3.12 changes

[sandrobonazzola]

On Fedora 39 unit tests are failing on:

Traceback (most recent call last):
  File "/usr/bin/did", line 42, in <module>
    did.cli.main()
  File "/usr/lib/python3.12/site-packages/did/cli.py", line 199, in main
    custom_plugins = did.base.Config().plugins
                     ^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/did/base.py", line 102, in __init__
    self.parser.readfp(codecs.open(path, "r", "utf8"))
    ^^^^^^^^^^^^^^^^^^
AttributeError: 'ConfigParser' object has no attribute 'readfp'. Did you mean: 'read'?

as the already deprecated readfp has been dropped in Python 3.12.

[sandrobonazzola]

Fixed by #313