remove leftover Python2 compatibility hybridation

bitfield/admin.py

@@ -1,5 +1,4 @@
 import django
-import six
 
 from django.core.exceptions import ValidationError
 if django.VERSION < (2, 0):
@@ -29,7 +28,7 @@ def __init__(self, field, request, params, model, model_admin, field_path):
     def queryset(self, request, queryset):
         filter_kwargs = dict(
             (p, BitHandler(v, ()))
-            for p, v in six.iteritems(self.used_parameters)
+            for p, v in self.used_parameters.items()
         )
         if not filter_kwargs:
             return queryset

bitfield/models.py

@@ -1,7 +1,3 @@
-from __future__ import absolute_import
-
-import six
-
 from django.db.models import signals
 from django.db.models.fields import Field, BigIntegerField
 
@@ -154,7 +150,7 @@ def to_python(self, value):
             # Regression for #1425: fix bad data that was created resulting
             # in negative values for flags.  Compute the value that would
             # have been visible ot the application to preserve compatibility.
-            if isinstance(value, six.integer_types) and value < 0:
+            if isinstance(value, int) and value < 0:
                 new_value = 0
                 for bit_number, _ in enumerate(self.flags):
                     new_value |= (value & (2 ** bit_number))

bitfield/types.py

@@ -1,8 +1,3 @@
-from __future__ import absolute_import
-
-from six import string_types
-
-
 def cmp(a, b):
     return (a > b) - (a < b)
 
@@ -238,7 +233,7 @@ def iteritems(self):
             yield (k, getattr(self, k).is_set)
 
     def get_label(self, flag):
-        if isinstance(flag, string_types):
+        if isinstance(flag, str):
             flag = self._keys.index(flag)
         if isinstance(flag, Bit):
             flag = flag.number

setup.py

@@ -31,7 +31,6 @@ def visit_Assign(self, node):
     zip_safe=False,
     install_requires=[
         'Django>=1.11.29',
-        'six',
     ],
     extras_require={
         'tests': [