refined NotFoundError doc

README.mdown

@@ -133,6 +133,10 @@ have the following objects available:
 >    imports and doesn't break there. You probably don't want to use this
 >    function. It's mostly for testing.
 
+`NotFoundError`
+>    If you use the goto function and no valid identifier (name) is at the
+>    place of the cursor (position). It will raise this exception.
+
 `set_debug_function`
 >    Sets a callback function for `debug.py`. This function is called with
 >    multiple text objects, in python 3 you could insert `print`.

functions.py

@@ -9,7 +9,6 @@ import debug
 import imports
 import os
 
-# TODO remove NotFoundError, should not be exposed
 __all__ = ['complete', 'goto', 'get_definitions',
            'NotFoundError', 'set_debug_function']
 

plugin/jedi.vim

@@ -88,7 +88,7 @@ if 1:
     try:
         definitions = functions.goto(source, row, column, buf_path)
     except functions.NotFoundError:
-        echo_highlight("Couldn't find a place to goto.")
+        echo_highlight("Cannot follow nothing. Put your cursor on a valid name.")
     except Exception:
         # print to stdout, will be in :messages
         echo_highlight("Some different eror, this shouldn't happen.")