Currently if valid swagger syntax is used for model composition an
error will be thrown due to the lack of a type property. This was
corrected by making object the default type.
schema_type = schema_deref.get('type', 'object')
I changed the swagger definition to test for this. Now PetCreate is a
composite of PetCreatePartOne and PetCreatePartTwo. However, this
caused `test_post_pets_empty_body` to fail, which turned out to be a
bug in the required properties.
In `_unmarshal_object` the `get_all_properties` method is called to get
all properties from the subschemas. However, this is not done for
required properties, meaning that only top level required properties
will be correctly validated. I have added a
`get_all_required_properties’ to fix this.
This caused `test_get_pets` to fail. In this case the bug allowed an
incorrect test case to be introduced. Pet requires `id`, but it also
requires name because it inherits from PetCreate. I have fixed this
test case by adding the missing required property.
After these changes `test_get_pet_not_found` failed due to a string
formatting error (double quotes vs single quotes). I fixed this by
switching to dictionary comparisons.
