Support form element attributes with no value

[sneethling@…]

There are a couple of form attributes such as required that was introduced in HTML5 that should not contain a value. For exaple required="required" is valid but for example required="true" will result in failed validation with true being marked as a bad value.

The correct use would be:

<input type="email" required />

Currently in forms.py attributes cannot be specified without a value which rely on the author knowing that a value of 'true' not being valid but 'required' being ok. it would be great if Django supports valueless attributes.

Perhaps doing:

widget=forms.TextInput(
    attrs={
        'required': ''
}))

will result in an input of:

<input type="text" required />

[Claude Paroz]

Description reformatted, please use preview when posting.