Drop unused import in unittest package.

Lib/unittest/case.py

@@ -9,8 +9,7 @@ import warnings
 import collections
 
 from . import result
-from .util import (strclass, safe_repr, sorted_list_difference,
-                   unorderable_list_difference, _count_diff_all_purpose,
+from .util import (strclass, safe_repr, _count_diff_all_purpose,
                    _count_diff_hashable)
 
 __unittest = True

Lib/unittest/main.py

@@ -2,7 +2,6 @@
 
 import sys
 import os
-import types
 
 from . import loader, runner
 from .signals import installHandler

Lib/unittest/result.py

 """Test result object"""
 
-import os
 import io
 import sys
 import traceback

Lib/unittest/test/_test_warnings.py

@@ -10,7 +10,6 @@ combinations of warnings args and -W flags and check that the output is correct.
 See #10535.
 """
 
-import io
 import sys
 import unittest
 import warnings