Fix multiple-inheritance object creation issue.

fsl/data/mesh.py

@@ -144,6 +144,14 @@ class Mesh(notifier.Notifier, meta.Meta):
     """
 
 
+    def __new__(cls, *args, **kwargs):
+        """Create a ``Mesh``. We must override ``__new__``, otherwise the
+        :class:`Meta` and :class:`Notifier` ``__new__`` methods will not be
+        called correctly.
+        """
+        return super(Mesh, cls).__new__(cls, *args, **kwargs)
+
+
     def __init__(self,
                  indices,
                  name='mesh',

fsl/utils/meta.py

@@ -27,8 +27,13 @@ class Meta(object):
        setMeta
     """
 
-    def __init__(self):
-        self.__meta = collections.OrderedDict()
+    def __new__(cls, *args, **kwargs):
+        """Initialises a ``Meta`` instance. """
+
+        new        = super(Meta, cls).__new__(cls)
+        new.__meta = collections.OrderedDict()
+
+        return new
 
 
     def metaKeys(self):

fsl/utils/notifier.py

@@ -94,7 +94,7 @@ class Notifier(object):
         instance.
         """
 
-        new = object.__new__(cls)
+        new = super(Notifier, cls).__new__(cls)
 
         # Listeners are stored in this
         #