Fix errors from pycodestyle.

biscuit/core/mixins.py

@@ -16,13 +16,13 @@ class ExtensibleModel(object):
     in every app is executed. All code that shall be injected into a model goes there.
 
     :Example:
-    
+
     .. code-block:: python
 
        from datetime import date, timedelta
 
        from biscuit.core.models import Person
-       
+
        @Person.property
        def is_cool(self) -> bool:
            return True

biscuit/core/templatetags/data_helpers.py

-from typing import Dict, Any
+from typing import Any
 
 from django import template
 

biscuit/core/util/core_helpers.py

 from importlib import import_module
 import pkgutil
-from typing import Optional, Sequence
+from typing import Sequence
 
 from django.http import HttpRequest
 

biscuit/core/views.py

-import requests
-from typing import Callable, Optional
+from typing import Optional
 
 from django.contrib.auth.decorators import login_required
 from django.http import Http404, HttpRequest, HttpResponse