Merge pull request #1948 from tkf/ast_node_interactivity_help

Fix help string for InteractiveShell.ast_node_interactivity

IPython/core/interactiveshell.py

@@ -371,7 +371,7 b' class InteractiveShell(SingletonConfigurable):'
     ast_node_interactivity = Enum(['all', 'last', 'last_expr', 'none'],
                                   default_value='last_expr', config=True, 
                                   help="""
-        'all', 'last', 'last_expr' or 'none'," specifying which nodes should be
+        'all', 'last', 'last_expr' or 'none', specifying which nodes should be
         run interactively (displaying output from expressions).""")
 
     # TODO: this part of prompt management should be moved to the frontends.