python - sqlalchemy.exc.ArgumentError: Can't load plugin: sqlalchemy.dialects:driver -

I'm trying to run the alembic migration and when I run < Pre> alembic revision --autogenerate -m "Added initial tables"

This fails to say

  sqlalchemy.exc.ArgumentError : Plugin can not be loaded: Sqlalchemy.dialects: driver   
 is the database url  
  postgresql + psycopg2: // dev: passwd @ localhost / Db   
 and I have  psycopg2  installed in my VirtualWhen  
  $ yolk -l flask-login - 0.1.3 - Active Flask-SQLLame - 0.16 - Active Flask - 0.9 - Active Ginja 2 - 2.6 - Active Mac - 0.7.3 - Active Markup - 0.15 - Active Python - 2.7.2 - Active Development (/ System / Library / Framework / Python Framework / Version -2.7 / lib / dynload) 7 / lib-dynload SQLAlchemy - 0.8.0 - Active Werkzeug - 0.8.3 - Active alabic - 0.4.2 - active antiorm - 1.1.1 - Active apps - 1.0.1 - active Distribution - 0.6.27 - Active Messenger - 0.0.2 - Active OSScript - 0.0.4 - AC Tive pep8 - 1.4.5 - Active Pipe - 1.1 - Active psycopg2 - 2.4.6 - Active wsgiref - 0.1.2 - Active Development (/ System / Library / Framework / Python.framework / Versions / 2.7 / lib / python2.7) Yolk - 0.4.3 - Active   
 Could this cause the problem?   
 
 
 Here's how to generate an error:  
  & Gt; & Gt; & Gt; Secularic import * * & Gt; & Gt; Traceback (most recent call final): ... etc sqlalchemy.exc.ArgumentError: plugin can not be loaded: sqlalchemy.dialects: driver   
 I can say that you In fact, you are not using postgrascape URLs, you think you are - you're probably calling a default-generated alembic.ini.