Impacted versions:10

Steps to reproduce:
Following the code in https://www.odoo.com/documentation/10.0/api_integration.html both in a fresh install and against 'https://demo.odoo.com/start' trows a type error

Current behavior:
Now I get an error when executing:

```
ids = models.execute_kw(db, uid, password,  'res.partner', 'search',
    [[['is_company', '=', True], ['customer', '=', True]]],
    {'limit': 1})
[record] = models.execute_kw(db, uid, password,
    'res.partner', 'read', [ids])
# count the number of fields fetched by default
len(record)
```

In particular it seems to be a type error (cannot marshal class odoo.tools.float_utils.float_precision)

Expected behavior:
I would expect it to behave as in the documentation

""" Return a dictionary that describes the field ``self``. """
        desc = {'type': self.type}
        for attr, prop in self.description_attrs:
            value = getattr(self, prop)
            if callable(value):
                value = value(env)
            if value is not None:
                desc[attr] = value
        return desc
    
    _description_store = property(attrgetter('store'))
    _description_manual = property(attrgetter('manual'))
    _description_depends = property(attrgetter('depends'))
    _description_related = property(attrgetter('related'))
    _description_company_dependent = property(attrgetter('company_dependent'))
    _description_readonly = property(attrgetter('readonly'))
    _description_required = property(attrgetter('required'))
    _description_states = property(attrgetter('states'))
    _description_groups = property(attrgetter('groups'))
    _description_change_default = property(attrgetter('change_default'))
    _description_deprecated = property(attrgetter('deprecated'))
    @property
    def _description_searchable(self):