title: How do I correct this sqlalchemy.exc.NoForeignKeysError?
body: <p>Why do I get the TraceBack</p>
  
  <pre><code>sqlalchemy.exc.NoForeignKeysError: Could not determine join condition
  between parent/child tables on relationship County.Legislators - 
  there are no foreign keys linking these tables.
  
  Ensure that referencing columns are associated with a
  ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression.
  </code></pre>
  
  <p>with the following models:</p>
  
  <pre><code>class County(Base):
      __tablename__ = 'tblCounty'
      CountyCode = Column('CountyCode', String, primary_key=True)
      Legislators = relationship('Legislators', backref='County', lazy='dynamic')
  
  class Legislators(Base):
      __tablename__ = 'VLegislators'
      EmployeeNo = Column('EmployeeNo', String, primary_key=True)
      CountyCode = Column('CountyCode', String, ForeignKey('County.CountyCode'))
  </code></pre>
  
  <p>I'm trying to map a public facing MS SQL database provided by the State of New Hampshire.  So no schema changes allowed.  </p>
  
  <p>Why does it complain about the lack of a ForeignKey relation when one is clearly defined in class Legislators?</p>