The error message changed to:

`'<' not supported between instances of 'foo' and 'bar'`

primaryjoin of a relationship involved comparison to an unhashable
type such as an HSTORE, lazy loads would fail due to a hash-oriented
check on the statement parameters, modified in 1.0 as a result of
:ticket:`3061` to use hashing and modified in :ticket:`3368`
to occur in cases more common than "load on pending".
The values are now checked for the ``__hash__`` attribute beforehand.
fixes #3416

now be constructed such that the visit methods receive an indication
of the owning expression object, if any.  Any visit method that
accepts keyword arguments (e.g. ``**kw``) will in most cases
receive a keyword argument ``type_expression``, referring to the
expression object that the type is contained within.  For columns
in DDL, the dialect's compiler class may need to alter its
``get_column_specification()`` method to support this as well.
The ``UserDefinedType.get_col_spec()`` method will also receive
``type_expression`` if it provides ``**kw`` in its argument
signature.
fixes #3074

for memoization on a class that uses slots.
- apply many more __slots__.  mem use for nova now at 46% savings

through all possible set values

that are now affixed to _MapperConfig
- declarative now creates column copies ahead of time
so that they are ready to go for a declared_attr
- overhaul of declared_attr; memoization, cascading modifier
- A relationship set up with :class:`.declared_attr` on
a :class:`.AbstractConcreteBase` base class will now be configured
on the abstract base mapping automatically, in addition to being
set up on descendant concrete classes as usual.
fixes #2670
- The :class:`.declared_attr` construct has newly improved
behaviors and features in conjunction with declarative.  The
decorated function will now have access to the final column
copies present on the local mixin when invoked, and will also
be invoked exactly once for each mapped class, the returned result
being memoized.   A new modifier :attr:`.declared_attr.cascading`
is added as well. fixes #3150
- the original plan for #3150 has been scaled back; by copying
mixin columns up front and memoizing, we don't actually need
the "map properties later" thing.
- full docs + migration notes

N occurrences of a parameterized string.   This allows parameterized
warnings that can refer to their arguments to be delivered a fixed
number of times until allowing Python warning filters to squelch them,
and prevents memory from growing unbounded within Python's
warning registries.
fixes #3178