Close cursor in custom SQL example

[Chris Jerdonek]

It would be better if ​here in this example, the cursor were explicitly closed (e.g. by using with connection.cursor() as cursor):

def my_custom_sql(self):
    cursor = connection.cursor()

    cursor.execute("UPDATE bar SET foo = 1 WHERE baz = %s", [self.baz])

    cursor.execute("SELECT foo FROM bar WHERE baz = %s", [self.baz])
    row = cursor.fetchone()

    return row

[Tim Graham]

Is there any advantage to also updating the PollManager example in topics/db/managers.txt?

[Claude Paroz <claude@…>]

In ccf7adb:

Fixed #27172 -- Closed database cursor explicitly in two doc examples

[Claude Paroz <claude@…>]

In d923733:

[1.10.x] Fixed #27172 -- Closed database cursor explicitly in two doc examples

Backport of ccf7adb064a70eb1b1ec5857f1dd54988f5c983c from master.