[1.5.x] Fixed #20025 -- Pointed to a MySQLdb fork for Python 3.

Made a few minor compatibility adjustments.

Backport of e81e319f from master.

django/db/backends/mysql/base.py

@@ -383,8 +383,9 @@ class DatabaseWrapper(BaseDatabaseWrapper):
             kwargs = {
                 'conv': django_conversions,
                 'charset': 'utf8',
-                'use_unicode': True,
             }
+            if not six.PY3:
+                kwargs['use_unicode'] = True
             settings_dict = self.settings_dict
             if settings_dict['USER']:
                 kwargs['user'] = settings_dict['USER']

django/db/backends/mysql/validation.py

@@ -10,6 +10,7 @@ class DatabaseValidation(BaseDatabaseValidation):
         from django.db import models
         varchar_fields = (models.CharField, models.CommaSeparatedIntegerField,
                 models.SlugField)
-        if isinstance(f, varchar_fields) and f.max_length > 255 and f.unique:
+        if (isinstance(f, varchar_fields) and f.unique
+                and (f.max_length is None or int(f.max_length) > 255)):
             msg = '"%(name)s": %(cls)s cannot have a "max_length" greater than 255 when using "unique=True".'
             errors.add(opts, msg % {'name': f.name, 'cls': f.__class__.__name__})

docs/ref/databases.txt

@@ -209,6 +209,15 @@ required for full MySQL support in Django.
 
 .. _MySQLdb: http://sourceforge.net/projects/mysql-python
 
+Python 3
+--------
+
+At the time of writing, the latest release of MySQLdb (1.2.4) doesn't support
+Python 3. In order to use MySQL under Python 3, you'll have to install an
+unofficial fork, such as `MySQL-for-Python-3`_.
+
+.. _MySQL-for-Python-3: https://github.com/clelland/MySQL-for-Python-3
+
 Creating your database
 ----------------------
 
@@ -318,8 +327,8 @@ Here's a sample configuration which uses a MySQL option file::
     default-character-set = utf8
 
 Several other MySQLdb connection options may be useful, such as ``ssl``,
-``use_unicode``, ``init_command``, and ``sql_mode``. Consult the
-`MySQLdb documentation`_ for more details.
+``init_command``, and ``sql_mode``. Consult the `MySQLdb documentation`_ for
+more details.
 
 .. _MySQL option file: http://dev.mysql.com/doc/refman/5.0/en/option-files.html
 .. _MySQLdb documentation: http://mysql-python.sourceforge.net/