Fix #379: Regression with Any and required

In 0.9.3, the `Schema`s associated to the `Any` validators where setup with the
`required` argument given to `Any`

https://github.com/alecthomas/voluptuous/blob/0.9.3/voluptuous/validators.py#L218

This allow us to write something like:

```
Schema(Any({'a': int}, {'b': str}, required=True))
```

In recent version, the `required` keyword is ignored.

This patch pass the required argument to the `Schema`s associated with the
`SubValidator`.

voluptuous/tests/tests.py

@@ -1322,3 +1322,30 @@ def test_strip_util_handles_various_inputs():
     assert Strip(u"3") == u"3"
     assert Strip(b'\xe2\x98\x83'.decode("UTF-8")) == b'\xe2\x98\x83'.decode("UTF-8")
     assert Strip(u" aaa ") == u"aaa"
+
+
+def test_any_required():
+    schema = Schema(Any({'a': int}, {'b': str}, required=True))
+
+    try:
+        schema({})
+    except MultipleInvalid as e:
+        assert_equal(str(e),
+                     "required key not provided @ data['a']")
+    else:
+        assert False, "Did not raise Invalid for MultipleInvalid"
+
+
+def test_any_required_with_subschema():
+    schema = Schema(Any({'a': Any(float, int)},
+                        {'b': int},
+                        {'c': {'aa': int}},
+                    required=True))
+
+    try:
+        schema({})
+    except MultipleInvalid as e:
+        assert_equal(str(e),
+                     "required key not provided @ data['a']")
+    else:
+        assert False, "Did not raise Invalid for MultipleInvalid"

voluptuous/validators.py

@@ -192,12 +192,13 @@ class _WithSubValidators(object):
     def __init__(self, *validators, **kwargs):
         self.validators = validators
         self.msg = kwargs.pop('msg', None)
+        self.required = kwargs.pop('required', False)
 
     def __voluptuous_compile__(self, schema):
-        self._compiled = [
-            schema._compile(v)
-            for v in self.validators
-        ]
+        self._compiled = []
+        for v in self.validators:
+            schema.required = self.required
+            self._compiled.append(schema._compile(v))
         return self._run
 
     def _run(self, path, value):