diff --git a/nbformat/tests/test_validator.py b/nbformat/tests/test_validator.py
index c79ab202..98096369 100644
--- a/nbformat/tests/test_validator.py
+++ b/nbformat/tests/test_validator.py
@@ -5,17 +5,17 @@
 
 import os
 import re
-
-from nbformat.warnings import MissingIDFieldWarning
 from copy import deepcopy
 
-from .base import TestsBase
+import pytest
 from jsonschema import ValidationError
+
 from nbformat import read
-from ..validator import isvalid, validate, iter_validate
-from ..json_compat import VALIDATORS
+from nbformat.warnings import MissingIDFieldWarning
 
-import pytest
+from ..json_compat import VALIDATORS
+from ..validator import isvalid, iter_validate, validate
+from .base import TestsBase
 
 nb4 = ("test4.ipynb", "test4.5.ipynb")
 
diff --git a/nbformat/validator.py b/nbformat/validator.py
index 19acf83f..b359b656 100644
--- a/nbformat/validator.py
+++ b/nbformat/validator.py
@@ -2,6 +2,7 @@
 # Distributed under the terms of the Modified BSD License.
 
 from __future__ import print_function
+
 import json
 import os
 import pprint
@@ -10,9 +11,10 @@
 from copy import deepcopy
 
 from ipython_genutils.importstring import import_item
-from .json_compat import get_current_validator, ValidationError
-from .reader import get_version, reads
+
 from .corpus.words import generate_corpus_id
+from .json_compat import ValidationError, get_current_validator
+from .reader import get_version, reads
 from .warnings import MissingIDFieldWarning
 
 validators = {}