SQLAlchemy (declarative) not creating db or tables

I am trying to use postgreSQL with SQLAlchemy. I having some issues because I am a new to SQLAlchemy, and may have misunderstood the documentation.

When I follow the documentation with SQLite I have no problems creating the database and the relations from the classes I specify. However, when I try to do it with Postgre I can't generate the relations or the db, instead I have to create the schemas and the tables manually in the shell.

This is what I currently have:

postgres_url = 'postgresql+psycopg2://some_user:some_password@localhost:5432/testdb'

engine = create_engine(postgres_url)

DB_session = sessionmaker(bind=engine)
db_session = DB_session()

Base = declarative_base()

Base.metadata.create_all(bind=engine)

#-----------------------------------------------------------
#                       User Entity
#-----------------------------------------------------------


class User(Base):

    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    fname = Column(String(45))
    lname = Column(String(45))
    token = Column(String(45))

    def __init__(self, fname, lname, token):
        self.fname = fname
        self.lname = lname
        self.token = token

    def __repr__(self):
        return 'Token: %s' % self.token

When I run the above code after manually creating the db I get a relation "users" does not exist, however, if I create the schema manually everything runs ok. I would appreciate a push in the right direction.