[Sqlalchemy-tickets] Issue #4116: Accessing AssociationProxy of aliased model breaks it (zzzeek/sqlalchemy)

[dima-starosud <iss...@bi...>]

New issue 4116: Accessing AssociationProxy of aliased model breaks it
https://bitbucket.org/zzzeek/sqlalchemy/issues/4116/accessing-associationproxy-of-aliased

dima-starosud:

This is using sqlalchemy 1.2.0b3.
When `AssociationProxy` is first accessed on `aliased` it leads to setting `owning_class` to that `AliasedClass`, which then leads to exceptions inside lib.
Please see details in following code snippet.

```
#!python

        class A(Base):
            __tablename__ = 'a'
            id = Column(Integer, primary_key=True)
            value = Column(String)

        class B(Base):
            __tablename__ = 'b'
            id = Column(Integer, primary_key=True)
            a_id = Column(Integer, ForeignKey(A.id))
            a = relationship(A)
            a_value = association_proxy('a', 'value')

        print(aliased(B).a_value)  # Due to this call line below fails
        print(B(a=A(value=4)).a_value)  # Class object expected, got '<AliasedClass at 0x7f491cbb3048; B>'.

```