Allow field attributes which are lists to validate the type of the list items

Starting to apply this for tags too, however it is not correcting things
as would be expected.

lib/ansible/playbook/attribute.py

@@ -21,12 +21,13 @@ __metaclass__ = type
 
 class Attribute:
 
-    def __init__(self, isa=None, private=False, default=None, required=False):
+    def __init__(self, isa=None, private=False, default=None, required=False, listof=None):
 
        self.isa = isa
        self.private = private
        self.default = default
        self.required = required
+       self.listof = listof
 
 class FieldAttribute(Attribute):
     pass

lib/ansible/playbook/base.py

@@ -274,6 +274,10 @@ class Base:
                     elif attribute.isa == 'list':
                         if not isinstance(value, list):
                             value = [ value ]
+                        if attribute.listof is not None:
+                            for item in value:
+                                if not isinstance(item, attribute.listof):
+                                    raise AnsibleParserError("the field '%s' should be a list of %s, but the item '%s' is a %s" % (name, attribute.listof, item, type(item)), obj=self.get_ds())
                     elif attribute.isa == 'dict' and not isinstance(value, dict):
                         raise TypeError()
 

lib/ansible/playbook/taggable.py

@@ -19,6 +19,8 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
+from six import string_types
+
 from ansible.errors import AnsibleError
 from ansible.playbook.attribute import FieldAttribute
 from ansible.template import Templar
@@ -26,7 +28,7 @@ from ansible.template import Templar
 class Taggable:
 
     untagged = set(['untagged'])
-    _tags = FieldAttribute(isa='list', default=[])
+    _tags = FieldAttribute(isa='list', default=[], listof=(string_types,int))
 
     def __init__(self):
         super(Taggable, self).__init__()