How can i assign validators to a behavior wich is assigned at runtime?

Plone Support Add-on Development
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1

My use case: in a setuphandler i iterate over all DX-Type defintions and add a behavior. That's ok and do what i need:

# setuphandlers.py 

def add_taxonomy_to_fti(context):

    taxonomy = schema.Set(
        title=_("taxonomy_studiengang"),
        description=_("Select Course and Semester"),
        required=False,
        value_type=schema.Choice(
            vocabulary="collective.taxonomy.taxonomies",
        ),
    )
    portal = api.portal.get()
    portal_types = portal.portal_types
    _behavior = "collective.taxonomy.generated.studienablauf"

    for dxtype in TYPES_FOR_TAXONOMY:

        fti = portal_types.get(dxtype)

        if _behavior in list(fti.behaviors):
            continue

        fti.behaviors = fti.behaviors + (_behavior,)
        typeschema = fti.lookupSchema()
        schemaeditor = IEditableSchema(typeschema)
        fieldname = "taxonomy_studienablauf"
        
        try:
            schemaeditor.removeField(fieldname)
        except ValueError:
            logger.info(
                "Fieldname for Taxonomy not found {} {}".format(dxtype, fieldname)
            )
        finally:
            notify(FieldRemovedEvent(fti, taxonomy))

        notify(SchemaInvalidatedEvent(portal_type=dxtype))

        schemaeditor.addField(
            taxonomy,
            name=fieldname,
        )
        notify(ObjectAddedEvent(taxonomy, typeschema))
        notify(FieldAddedEvent(fti, taxonomy))
        notify(SchemaInvalidatedEvent(portal_type=dxtype))

# validators.py
from collective.taxonomy.interfaces import ITaxonomySelectWidget
from z3c.form import validator
from z3c.form.interfaces import IOrderedSelectWidget
from z3c.form.validator import SimpleFieldValidator
from zope.component import provideAdapter
from zope.interface import Invalid


class CourseOfStudiesValidator(SimpleFieldValidator):
    """z3c.form validator class for studiumsablauf taxonomy"""

    def validate(self, value):

        print("in my validation method")

        """Validate selected items count from the list, should be greater zero"""
        super(CourseOfStudiesValidator, self).validate(value)
        if not value:
            raise Invalid("My custom error message")


validator.WidgetValidatorDiscriminators(
    CourseOfStudiesValidator, widget=IOrderedSelectWidget
)

validator.WidgetValidatorDiscriminators(
    CourseOfStudiesValidator, widget=ITaxonomySelectWidget
)

provideAdapter(CourseOfStudiesValidator)

My Validator doesn't match. I didn't see the print statement if i submit the Add Form. My Question is: how can i assign a validator?