I got it! I return’ed app and admin in create_app(), which caused the problem. And it seems that’s also where the mysterious Tuple was situated. If create_app() only return’s app my app starts as it should. Now to work out how to run flask-admin correctly. Corrected code for now: init.py:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from flask_admin import Admin
from flask_bootstrap import Bootstrap
from flask_security import Security, SQLAlchemyUserDatastore
from flask_mail import Mail
import logging
from logging.handlers import SMTPHandler, RotatingFileHandler
import os
from config import Config

db = SQLAlchemy()
migrate = Migrate()
bootstrap = Bootstrap()
from app.models import User, Role
user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security()
mail = Mail()
admin = Admin()

def create_app(config_class=Config):
    app=Flask(__name__)
    app.config.from_object(Config)

    db.init_app(app)
    migrate.init_app(app, db)
    from app.models import User, Role
    user_datastore = SQLAlchemyUserDatastore(db, User, Role)
    security.init_app(app, user_datastore)
    bootstrap.init_app(app)
    mail.init_app(app)


    app.config['FLASK_ADMIN_SWATCH'] = 'cerulean'

    from app.errors import bp as errors_bp
    app.register_blueprint(errors_bp)

    from app.main import bp as main_bp
    app.register_blueprint(main_bp)

    admin = Admin(app, name='werda', template_mode='bootstrap3')

    #send errors via mail:
    if not app.debug:
        if app.config['MAIL_SERVER']:
            auth = None
            if app.config['MAIL_USERNAME'] or app.config['MAIL_PASSWORD']:
                auth = (app.config['MAIL_USERNAME'], app.config['MAIL_PASSWORD'])
            secure = None
            if app.config['MAIL_USE_TLS']:
                secure = ()
            mail_handler = SMTPHandler(
                mailhost=(app.config['MAIL_SERVER'], app.config['MAIL_PORT']),
                fromaddr='[email protected]' + app.config['MAIL_SERVER'],
                toaddrs=app.config['ADMINS'], subject='werda Failure',
                credentials=auth, secure=secure)
            mail_handler.setLevel(logging.ERROR)
            app.logger.addHandler(mail_handler)
        #save errors to log file:
        if not os.path.exists('logs'):
            os.mkdir('logs')
        file_handler = RotatingFileHandler('logs/werda.log', maxBytes=10240,
                                        backupCount=10)
        file_handler.setFormatter(logging.Formatter(
            '%(asctime)s %(levelname)s: %(message)s [in %(pathname)s:%(lineno)d]'))
        file_handler.setLevel(logging.INFO)
        app.logger.addHandler(file_handler)

        app.logger.setLevel(logging.INFO)
        app.logger.info('werda startup')

    return app #deleted admin here

from app import models