When you have Custom Connection and use SelectField, Connection screen becomes unusable (see #17064) 

We should detect the situation and throw an exception when Provider Info is initialized.
airflow/providers_manager.py
#
#
#
"""Manages all providers."""
import fnmatch
import importlib
import json
import logging
import os
from collections import OrderedDict
from typing import Any, Dict, NamedTuple, Set
import jsonschema
from wtforms import Field
from airflow.utils import yaml
from airflow.utils.entry_points import entry_points_with_dist
try:
    import importlib.resources as importlib_resources
except ImportError:
    
    import importlib_resources
log = logging.getLogger(__name__)
def _create_provider_info_schema_validator():