a function to check if the definition is in a builtin module

functions.py

@@ -98,6 +98,9 @@ class Definition(object):
 
         return str(par.path)
 
+    def in_builtin_module(self):
+        return not self.module_path.endswith('.py')
+
     @property
     def line_nr(self):
         return self.definition.start_pos[0]

plugin/jedi.vim

@@ -98,6 +98,9 @@ if 1:
             vim.command('normal! m`')
 
             d = definitions[0]
+            if d.in_builtin_module():
+                echo_highlight("Builtin modules cannot be displayed.")
+            else:
                 if d.module_path != vim.current.buffer.name:
                     if vim.eval('g:jedi#use_tabs_not_buffers') == '1':
                         vim.command('call jedi#tabnew("%s")' % d.module_path)