Failing validation for new resources with reference

[Sergey Kraynev]

Fix for bug #1192142 covers only resources which return None value during resolve get_resource function. Unfortunately there are some resources, which may return u'None' or their name.
You may check it follow steps below:
- add network constraint for port resource

         NETWORK: properties.Schema(
             properties.Schema.STRING,
- _('Network this port belongs to.')
+ _('Network this port belongs to.'),
+ constraints=[
+ constraints.CustomConstraint('neutron.network')
+ ]
+
         ),

- Create template with two resources with reference:

heat_template_version: 2013-05-23

resources:
  private_net:
    type: OS::Neutron::Net
    properties:
      name: private_net_name

  port1:
    type: OS::Neutron::Port
    properties:
      name: name
      network: {get_resource: private_net}

- try to create stack using template above.

you will see next error:
ERROR: Property error : port1: network Error validating value u'None': Unable to find network with name 'None'

This problem affects other custom constraints in case, when we use reference on not created resource.

[Qiming Teng (tengqim)]

duplicated entry to #1347571.

[Sergey Kraynev (skraynev)]

Qiming , thank you that find this duplication. I don't know why I got two bugs... may be some problems during bug creation.