CREATE TABLE table_17593 ("Season" TEXT, "Serbian League Belgrade" TEXT, "Serbian League East" TEXT, "Serbian League Vojvodina" TEXT, "Serbian League West" TEXT)

What team was promoted in the Serbian League East in the same season when Kolubara was promoted in the Serbian League Belgrade?
SELECT "Serbian League East" FROM table_17593 WHERE "Serbian League Belgrade" = 'Kolubara'
SELECT "Serbian League East" FROM "table_17593" WHERE "Serbian League Belgrade" = 'Kolubara'