diff --git a/openapi_core/extensions/__init__.py b/openapi_core/extensions/__init__.py
index f73511c..5f89115 100644
--- a/openapi_core/extensions/__init__.py
+++ b/openapi_core/extensions/__init__.py
@@ -1 +1 @@
-"""OpenAPI extensions package"""
\ No newline at end of file
+"""OpenAPI extensions package"""
diff --git a/openapi_core/extensions/models/__init__.py b/openapi_core/extensions/models/__init__.py
index bf6ad29..68a0561 100644
--- a/openapi_core/extensions/models/__init__.py
+++ b/openapi_core/extensions/models/__init__.py
@@ -1 +1 @@
-"""OpenAPI X-Model extension package"""
\ No newline at end of file
+"""OpenAPI X-Model extension package"""
diff --git a/openapi_core/schema/parameters/models.py b/openapi_core/schema/parameters/models.py
index daacee2..62a3a39 100644
--- a/openapi_core/schema/parameters/models.py
+++ b/openapi_core/schema/parameters/models.py
@@ -2,7 +2,9 @@
 import logging
 import warnings
 
-from openapi_core.schema.parameters.enums import ParameterLocation, ParameterStyle
+from openapi_core.schema.parameters.enums import (
+    ParameterLocation, ParameterStyle,
+)
 from openapi_core.schema.parameters.exceptions import (
     MissingRequiredParameter, MissingParameter, InvalidParameterValue,
     EmptyParameterValue,
@@ -83,7 +85,7 @@ class Parameter(object):
             if not self.schema or self.schema.default is None:
                 raise MissingParameter(
                     "Missing `{0}` parameter".format(self.name))
-            
+
             raw = self.schema.default
 
         if self.aslist and self.explode:
diff --git a/openapi_core/schema/specs/factories.py b/openapi_core/schema/specs/factories.py
index 3a280b0..06868f6 100644
--- a/openapi_core/schema/specs/factories.py
+++ b/openapi_core/schema/specs/factories.py
@@ -4,8 +4,6 @@ from functools import lru_cache
 
 from openapi_spec_validator import openapi_v3_spec_validator
 
-from openapi_core.schema.operations.exceptions import InvalidOperation
-from openapi_core.schema.servers.exceptions import InvalidServer
 from openapi_core.schema.components.factories import ComponentsFactory
 from openapi_core.schema.infos.factories import InfoFactory
 from openapi_core.schema.paths.generators import PathsGenerator