[1.9.x] Fixed #25584 -- Documented a pip error when installing Django 1.9.

Backport of ee66d8dd7d from master

docs/releases/1.9.txt

@@ -1009,6 +1009,29 @@ a Django application with this structure::
         jquery.js
         jquery.min.js
 
+.. _syntax-error-old-pip-django-19:
+
+``SyntaxError`` when installing Django with pip ≤ 1.5.6
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When installing Django 1.9+ with pip ≤ 1.5.6, you'll see::
+
+    Compiling django/conf/app_template/apps.py ...
+      File "django/conf/app_template/apps.py", line 4
+        class {{ camel_case_app_name }}Config(AppConfig):
+              ^
+    SyntaxError: invalid syntax
+
+    Compiling django/conf/app_template/models.py ...
+      File "django/conf/app_template/models.py", line 1
+        {{ unicode_literals }}from django.db import models
+                                 ^
+    SyntaxError: invalid syntax
+
+It's safe to ignore these errors (Django will still install just fine), and you
+can avoid them by upgrading pip to a more recent version using
+``pip install -U pip``.
+
 Miscellaneous
 ~~~~~~~~~~~~~
 

docs/topics/install.txt

@@ -165,7 +165,8 @@ This is the recommended way to install Django.
 1. Install pip_. The easiest is to use the `standalone pip installer`_. If your
    distribution already has ``pip`` installed, you might need to update it if
    it's outdated. (If it's outdated, you'll know because installation won't
-   work.)
+   work. You might see some :ref:`harmless SyntaxErrors
+   <syntax-error-old-pip-django-19>` also.)
 
 2. Take a look at virtualenv_ and virtualenvwrapper_. These tools provide
    isolated Python environments, which are more practical than installing