"export_all_courses" management script fails on Django 1.8

Description

Django 1.8 uses `argparse` instead of `optparse` for management scripts so the use `*args` is discouraged. From the docs:

Changed in Django 1.8:
Before Django 1.8, management commands were based on the optparse module, and positional arguments were passed in *args while optional arguments were passed in **options. Now that management commands use argparse for argument parsing, all arguments are passed in **options by default, unless you name your positional arguments to args (compatibility mode). You are encouraged to exclusively use **options for new commands.

https://docs.djangoproject.com/en/1.8/howto/custom-management-commands/

But the `export_all_courses` is still reading input from `args`: https://github.com/edx/edx-platform/blob/master/cms/djangoapps/contentstore/management/commands/export_all_courses.py#L20-L23

So running the command will fail:

Steps to Reproduce

$ cd /edx/app/edxapp/edx-platform
$ python manage.py cms export_all_courses /tmp

Expected behavior: courses are exported to `/tmp` folder
Actual behavior: error message "manage.py export_all_courses: error: unrecognized arguments: /tmp"

Current Behavior

None

Expected Behavior

None

Reason for Variance

None

Release Notes

None

User Impact Summary

None

Assignee

Unassigned

Reporter

Luiz Aoqui

Labels

Reach

None

Impact

None

Platform Area

None

Customer

None

Partner Manager

None

URL

None

Contributor Name

None

Groups with Read-Only Access

None

Actual Points

None

Category of Work

None

Platform Map Area (Levels 1 & 2)

None

Platform Map Area (Levels 3 & 4)

None

Priority

CAT-3
Configure