Make Schema([]) usage consistent with Schema({})

Validation on an empty list was not raising any exception when given values
but an empty dict was. Make it uniform and make them both raise a
MultipleInvalid exception on unwanted values.

README.md

@@ -234,7 +234,7 @@ contain anything, specify it as `list`:
 ...   raise AssertionError('MultipleInvalid not raised')
 ... except MultipleInvalid as e:
 ...   exc = e
->>> str(exc) == "not a valid value"
+>>> str(exc) == "not a valid value @ data[1]"
 True
 >>> schema([])
 []

voluptuous/schema_builder.py

@@ -228,7 +228,7 @@ def _compile(self, schema):
             return self._compile_object(schema)
         if isinstance(schema, collections.Mapping):
             return self._compile_dict(schema)
-        elif isinstance(schema, list) and len(schema):
+        elif isinstance(schema, list):
             return self._compile_list(schema)
         elif isinstance(schema, tuple):
             return self._compile_tuple(schema)
@@ -551,6 +551,10 @@ def validate_sequence(path, data):
 
             # Empty seq schema, allow any data.
             if not schema:
+                if data:
+                    raise er.MultipleInvalid([
+                        er.ValueInvalid('not a valid value', [value]) for value in data
+                    ])
                 return data
 
             out = []