upd

app.py

@@ -12,6 +12,7 @@ app.config['SECRET_KEY'] = 'mysecretkey'
 db = SQLAlchemy(app)
 
 class Utente(db.Model):
+    __tablename__ = 'utente'
     id = db.Column(db.Integer, primary_key=True, autoincrement=True)
     nickname = db.Column(db.String(80), unique=True, nullable=False)
     username = db.Column(db.String(80), unique=True, nullable=False)
@@ -21,6 +22,7 @@ class Utente(db.Model):
     messaggi = db.relationship('Messaggio', back_populates='user', lazy='dynamic')
 
 class Messaggio(db.Model):
+    __tablename__ = 'messaggio'
     id = db.Column(db.Integer, primary_key=True)
     user_id = db.Column(db.Integer, db.ForeignKey('utente.id'), nullable=False)
     messaggio = db.Column(db.Text, nullable=False)