Remove Python 2 references from docs

docs/contributing/developing.rst

@@ -194,10 +194,7 @@ To start this simple server, run the following commands:
 .. code-block:: console
 
     $ cd docs/_build/html/
-    $ # Python 2
-    $ python2 -mSimpleHTTPServer 8080
-    $ # Python 3
-    $ python3 -mhttp.server 8080
+    $ python -mhttp.server 8080
 
 Now you can open <http://localhost:8080/> in your web browser to see the compiled documentation.
 

docs/reference/contrib/modeladmin/indexview.rst

@@ -91,7 +91,7 @@ You have three possible values that can be used in list_display:
 A few special cases to note about ``list_display``:
 
 -   If the field is a ``ForeignKey``, Django will display the output of
-    ``__str__()`` (``__unicode__()`` on Python 2) of the related object.
+    ``__str__()`` of the related object.
 
 -   If the string provided is a method of the model or ``ModelAdmin`` class,
     Django will HTML-escape the output by default. To escape user input and
@@ -163,7 +163,7 @@ A few special cases to note about ``list_display``:
                 return super(self, PersonAdmin).get_empty_value_display(field_name)
 
 
-    The ``__str__()`` (``__unicode__()`` on Python 2) method is just as valid
+    The ``__str__()`` method is just as valid
     in ``list_display`` as any other model method, so it’s perfectly OK to do
     this:
 

docs/topics/snippets.rst

@@ -16,7 +16,6 @@ Here's an example snippet model:
 .. code-block:: python
 
   from django.db import models
-  from django.utils.encoding import python_2_unicode_compatible
 
   from wagtail.wagtailadmin.edit_handlers import FieldPanel
   from wagtail.wagtailsnippets.models import register_snippet
@@ -24,7 +23,6 @@ Here's an example snippet model:
   ...
 
   @register_snippet
-  @python_2_unicode_compatible  # provide equivalent __unicode__ and __str__ methods on Python 2
   class Advert(models.Model):
       url = models.URLField(null=True, blank=True)
       text = models.CharField(max_length=255)