Enable OAuth token exchange only if OAuth provider

lms/urls.py

@@ -597,14 +597,19 @@ if settings.FEATURES.get('AUTOMATIC_AUTH_FOR_TESTING'):
 if settings.FEATURES.get('ENABLE_THIRD_PARTY_AUTH'):
     urlpatterns += (
         url(r'', include('third_party_auth.urls')),
+        # NOTE: The following login_oauth_token endpoint is DEPRECATED.
+        # Please use the exchange_access_token endpoint instead.
+        url(r'^login_oauth_token/(?P<backend>[^/]+)/$', 'student.views.login_oauth_token'),
+    )
+
+# OAuth token exchange
+if settings.FEATURES.get('ENABLE_THIRD_PARTY_AUTH') and settings.FEATURES.get('ENABLE_OAUTH2_PROVIDER'):
+    urlpatterns += (
         url(
             r'^oauth2/exchange_access_token/(?P<backend>[^/]+)/$',
             oauth_exchange.views.AccessTokenExchangeView.as_view(),
             name="exchange_access_token"
         ),
-        # NOTE: The following login_oauth_token endpoint is DEPRECATED.
-        # Please use the exchange_access_token endpoint instead.
-        url(r'^login_oauth_token/(?P<backend>[^/]+)/$', 'student.views.login_oauth_token'),
     )
 
 # Certificates Web/HTML View