title: Dropping constraint in SQLAlchemy
body: <p>I created a class in Pyramid-SQLAlchemy and my models.py contained the following:</p>
  
  <pre><code>class Students(Base):
  
      __tablename__ = 'students'
      id = Column(Integer, primary_key=True, nullable=False, autoincrement=True)
      name = Column(String(50, convert_unicode=True), nullable=False, unique=True)  
  </code></pre>
  
  <p>I accidentally created the <strong>unique</strong> constraint and ran the initializedb.py command, and the schemas were created. I tried removing the unique constraint and rerunning the initializedb.py command but the Constraint wouldn't drop and I get this error.</p>
  
  <pre><code>sqlalchemy.exc.IntegrityError: (IntegrityError) column name is not unique u'INSERT INTO students (id,name) VALUES (?, ?)' (200,'Hailey')
  </code></pre>
  
  <p>How do I drop/modify this constraint?</p>