Address style issues

scrapy/utils/response.py

@@ -61,7 +61,6 @@ _mime_overrides = get_data('scrapy', 'mime.types') or b''
 _MIME_TYPES.readfp(StringIO(_mime_overrides.decode()))
 
 
-
 def _is_html_mime_type(mime_type):
     if mime_type in {
         b'application/xhtml+xml',

tests/test_responsetypes.py

@@ -1,5 +1,4 @@
 import unittest
-from warnings import catch_warnings
 
 import pytest
 
@@ -10,7 +9,7 @@ from scrapy.http import (
     TextResponse,
     XmlResponse,
 )
-from scrapy.responsetypes import responsetypes, ResponseTypes
+from scrapy.responsetypes import responsetypes
 from .test_utils_response import (
     POST_XTRACTMIME_SCENARIOS,
     PRE_XTRACTMIME_SCENARIOS,