Avoid warning with jsonschema 4.16.0 (#1601)

Accessing jsonschema.draftN_format_checker is now deprecated

connexion/decorators/validation.py

@@ -8,7 +8,7 @@
 import logging
 import typing as t
 
-from jsonschema import Draft4Validator, ValidationError, draft4_format_checker
+from jsonschema import Draft4Validator, ValidationError
 from jsonschema.validators import extend
 from werkzeug.datastructures import FileStorage
 
@@ -22,6 +22,11 @@
 
 TYPE_MAP = {"integer": int, "number": float, "boolean": boolean, "object": dict}
 
+try:
+    draft4_format_checker = Draft4Validator.FORMAT_CHECKER
+except AttributeError:  # jsonschema < 4.5.0
+    from jsonschema import draft4_format_checker
+
 
 class TypeValidationError(Exception):
     def __init__(self, schema_type, parameter_type, parameter_name):