Tax-Calculator ParamTools crash when using marshmallow 3.22

[martinholmer]

When running Python 3.11 and using marshmallow 3.22, Tax-Calculator crashes with this error:

 File "/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/paramtools/schema.py", line 240, in load
    return self.validate_only(data)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/paramtools/schema.py", line 207, in validate_only
    if self._has_processors(decorators.VALIDATES_SCHEMA):
       ^^^^^^^^^^^^^^^^^^^^
AttributeError: 'ValidatorSchema' object has no attribute '_has_processors'. Did you mean: '_invoke_processors'?

Did marshmallow remove _has_processors in the 3.22 version?

We have been able to work around this by restricting the marshmallow version to be <3.22,
but it seems as if this is a bug in ParamTools.

cc: @MattHJensen @jdebacker @donboyd5

[martinholmer]

Fixed by PR #141.