class apitools.base.protorpclite.messages.Message is unhashable in Python 3

[ttanay]

The class apitools.base.protorpclite.messages.Message is an unhashable type in Python 3 and as a result, raises a TypeError when used as a key in a dict.

The reason for this is that in Python 3.x "a class that overrides __eq__() and does not define __hash__() will have its __hash__() implicitly set to None" (https://docs.python.org/3.6/reference/datamodel.html#object.__hash__). This makes it unhashable.

In Python 2, since __eq__() was defined, it simply inherited the __hash__() from object. In Python 3 it doesn't.