How to setup oauth2 SSO using auth-backends plugin

Hello everyone,
I’m trying to connect my own marketing site to my open edx instance using auth-backends.
I’ve added an application and set these values on my site:

INSTALLED_APPS = INSTALLED_APPS + ['social_django']

# Generic OAuth2 variables irrespective of SSO/backend service key types.
OAUTH2_PROVIDER_URL = 'http://edx.devstack.lms:18000/oauth2'

# OAuth2 variables specific to social-auth/SSO login use case.
SOCIAL_AUTH_EDX_OAUTH2_KEY = "mktg-client-id"
SOCIAL_AUTH_EDX_OAUTH2_SECRET = "mktg-client-secret"
SOCIAL_AUTH_EDX_OAUTH2_URL_ROOT = "http://localhost:18000"
SOCIAL_AUTH_EDX_OAUTH2_PUBLIC_URL_ROOT = "http://localhost:18000"
SOCIAL_AUTH_REDIRECT_IS_HTTPS = False
SOCIAL_AUTH_STRATEGY = "auth_backends.strategies.EdxDjangoStrategy"

AUTHENTICATION_BACKENDS = (
    'auth_backends.backends.EdXOAuth2',
    'django.contrib.auth.backends.ModelBackend',
)

Now when I reach the LMS and login, it redirects me to my site with this parameter included in the query string:

error=invalid_scope

I didn’t define any scope in my settings. Requested scopes is by default: user_id+profile+email

Any help is really appreciated

Could you kindly tell me that which version of auth-backends plugin can I use to connect my django site to an ironwood.master instance of Open edX?