A Custom Validator for NetBox 3.0+ to prevent sites from being retired if they have circuits that aren't deprovisioning or decommissioned.

site_circuit_validation.py

from extras.validators import CustomValidator
from circuits.models import Circuit


class SiteStatusCircuitValidator(CustomValidator):
    """
    Prevent sites from being retired if they have circuits that aren't in deprovisioning or decommissioned status.
    """
    def validate(self, site):
        circuit_count = Circuit.objects.filter(terminations__site=site).exclude(
            status__in=["deprovisioning", "decommissioned"]
        ).count()
        if site.status == "retired" and circuit_count > 0:
            self.fail(
                f"Site status cannot be set to 'retired', {circuit_count} circuits"
                "are not in deprovisioning or decommissioned status.",
                field="status",
            )