SchemaGenerator is not using the SCRIPT_NAME in the url

[bobkarreman]

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

Deploy your django project on a subpath with a proxy and make sure to set the SCRIPT_NAME header.

Expected behavior

Urls in the schema to be using the URLs with the SCRIPT_NAME prepended.

Actual behavior

URLs without the SCRIPT_NAME making the Django REST Swagger UI unusable, since its calling to the wrong URLs.

Also see this ticket at the Django REST Swagger repo: marcgibbons/django-rest-swagger#494 (comment)