MySQL (mariaDB) Connection Error with SqlAlchemy

Hello I have a mariaDB database on a Ubuntu server running in a virtual box. With 'Sequal Pro' i can connect without any problems (with the ssh option). Port forwarding like this: HOST 127.0.0.1 3306 GAST 10.0.2.15 3306

But in my python application i can't connect, or better it lost the connection before it can do something, with the following error:

OperationalError: (OperationalError) (2013, 'Lost connection to MySQL server during query') None None

I use SqlAlchemy with the mysqldb connector, like this: In the init.py file in models directory:

# for this must install pymsql (pip install pymysql)
DATABASE = 'mysql+pymysql://<user>:<password>@127.0.0.1/fist-test'

app.debug = DEBUG
app.secret_key = 'secret-key123'
app.config['SQLALCHEMY_DATABASE_URI'] = DATABASE
db = SQLAlchemy(app)

In the project main directory in the main.py file:

from models import db

@app.route('/test')
def test():
    db.create_all()
    return 'create objects...'

if __name__ == '__main__':
    app.run()

In models is also some model class:

from sqlalchemy import Column, Integer, String

class User(Base):
     __tablename__ = 'users'

     id = Column(Integer, primary_key=True)
     name = Column(String)
     fullname = Column(String)
     password = Column(String)

     def __init__(self, name, fullname, password):
         self.name = name
         self.fullname = fullname
         self.password = password

     def __repr__(self):
        return "<User('%s','%s', '%s')>" % (self.name, self.fullname, self.password)

Hope someone can help me to understand and solve the problem.

Thanks for your time!