Disallow creation of product version with empty version name.

A product version with version name equals to null/empty/blank is
implicitly created with the product.  This patch disallows users
to create versions with empty name.

Change-Id: Iad477e486e23415ce20a9cd9367b9ef1a97173a4

refstack/api/validators.py

@@ -250,3 +250,6 @@ class ProductVersionValidator(BaseValidator):
     def validate(self, request):
         """Validate product version data."""
         super(ProductVersionValidator, self).validate(request)
+        body = json.loads(request.body)
+
+        self.check_emptyness(body, ['version'])