Unittest: Compare max_size with column size of database

import unittest

from django.db import connection
from django.db.models.loading import get_models

class MaxLengthTest(unittest.TestCase):
    def testMaxLength(self):
        '''
        Compare max_length of model with size in the database.
        '''
        cursor=connection.cursor()
        errors=[]
        for cls in get_models():
            for field in cls._meta.fields:
                max_length=getattr(field, 'max_length', None)
                if not max_length:
                    continue
                column=field.db_column or field.column
                if not column:
                    continue
                cursor.execute('''SELECT "%s" from "%s" LIMIT 0''' % (column, cls._meta.db_table))
                for name, type_code, display_size, internal_size, precision, scale, null_ok in cursor.description:
                    if max_length!=internal_size:
                        errors.append('%s %s.%s Python Model max_length: %s Internal Size: %s' % (
                                cls, cls._meta.db_table, column, max_length, internal_size))
        if errors:
            raise Exception('\n'.join(errors))