- bpy.path.abspath(), added optional library argument since any paths from linked datablocks are relative to this, not the blend files path, this saves kludgy path code wherever libraries may be used.

- Image "Edit Externally" operator can now edit relative library images.

also minor edits to navmesh.

release/scripts/startup/bl_operators/image.py

@@ -69,8 +69,6 @@ class EditExternally(Operator):
             self.report({'ERROR'}, "Image path not set")
             return {'CANCELLED'}
 
-        filepath = os.path.normpath(bpy.path.abspath(filepath))
-
         if not os.path.exists(filepath):
             self.report({'ERROR'},
                         "Image path %r not found, image may be packed or "
@@ -93,15 +91,16 @@ class EditExternally(Operator):
         return {'FINISHED'}
 
     def invoke(self, context, event):
+        import os
         try:
-            filepath = context.space_data.image.filepath
-        except:
-            import traceback
-            traceback.print_exc()
-            self.report({'ERROR'}, "Image not found on disk")
+            image = context.space_data.image
+        except AttributeError:
+            self.report({'ERROR'}, "Context incorrect, image not found")
             return {'CANCELLED'}
 
-        self.filepath = filepath
+        filepath = bpy.path.abspath(image.filepath, library=image.library)
+
+        self.filepath = os.path.normpath(filepath)
         self.execute(context)
 
         return {'FINISHED'}