'Engine' object has no attribute 'drivername'

问题

Im integrate Flask and SQLAlchemy in my application, but can understand, why at login page in getting big stacktrace. This errors now I'll taking after switching to Mac OS from Debian. All used libraries in virtuaelnv.

I have right now these things:
1) in flask_app.py:

from flask import Flask, request, session
from flask_sqlalchemy import SQLAlchemy
from db import tables as dbTables
from db.queries import engine as db_engine

app = Flask(__name__, template_folder='./web/templates/', static_folder='./web/static/', static_url_path='')
app.config['SECRET_KEY'] = 'some_secret_key'
app.config['SQLALCHEMY_DATABASE_URI'] = db_engine
db_connection = SQLAlchemy(app)

import web.admin
import web.views

if __name__ == "__main__":
    from web.admin import *
    from web.views import *
    app.run(port=8500, debug=True)

2) Its my queries.py, which contains this strings and code for taking some data from PostgreSQL DB:

import datetime
from hashlib import sha256
from time import gmtime, strftime

import sqlalchemy
import sqlalchemy.exc
from sqlalchemy import and_, func, asc
from sqlalchemy.orm import sessionmaker

from tables import File as FileTable
from tables import Users, FileServer, FileSpace, Catalog

engine = sqlalchemy.create_engine("postgresql://dev:developer@localhost/csan", pool_size=20, max_overflow=0)
Session = sessionmaker(bind=engine)

# and some queries for DB
# ...

3) And this stacktrace, after sending to http://localhost:8500/admin/login POST request:

AttributeError
AttributeError: 'Engine' object has no attribute 'drivername'

Traceback (most recent call last)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_admin/base.py", line 62, in inner
return f(self, *args, **kwargs)
File "/Users/savicvalera/code/Helenae/Helenae/helenae/web/admin.py", line 42, in login_view
if helpers.validate_form_on_submit(form):
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_admin/helpers.py", line 47, in validate_form_on_submit
return is_form_submitted() and form.validate()
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/form.py", line 310, in validate
return super(Form, self).validate(extra)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/form.py", line 152, in validate
if not field.validate(self, extra):
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/fields/core.py", line 200, in validate
stop_validation = self._run_validation_chain(form, chain)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/fields/core.py", line 220, in _run_validation_chain
validator(form, self)
File "/Users/savicvalera/code/Helenae/Helenae/helenae/web/forms.py", line 19, in validate_login
user = get_user(self.login.data)
File "/Users/savicvalera/code/Helenae/Helenae/helenae/web/forms.py", line 11, in get_user
return db_connection.session.query(dbTables.Users).filter_by(name=user).first()
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/sqlalchemy/orm/scoping.py", line 150, in do
return getattr(self.registry(), name)(*args, **kwargs)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/sqlalchemy/util/_collections.py", line 910, in __call__
return self.registry.setdefault(key, self.createfunc())
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 139, in __init__
bind=db.engine,
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 780, in engine
return self.get_engine(self.get_app())
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 797, in get_engine
return connector.get_engine()
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 470, in get_engine
self._sa.apply_driver_hacks(self._app, info, options)
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 739, in apply_driver_hacks
if info.drivername.startswith('mysql'):
AttributeError: 'Engine' object has no attribute 'drivername'