Assert file exists on load in ReferenceLoader to avoid empty reference

colorbleed/maya/plugin.py

@@ -39,9 +39,12 @@ class ReferenceLoader(api.Loader):
              namespace=None,
              data=None):
 
+        import os
         from avalon.maya import lib
         from avalon.maya.pipeline import containerise
 
+        assert os.path.exists(self.fname), "%s does not exist." % self.fname
+
         asset = context['asset']
 
         namespace = namespace or lib.unique_namespace(