RemoteError._render_traceback_ calls self.render_traceback

rather than an alias

There are two options here:

1. `_render_traceback_`  should *call* render_traceback
2. any subclass that redefines render_traceback must also redefine `_render_traceback_`

I went with 1., which is more efficient code-wise when subclassing RemoteError
(would prevent future cases of this same mistake),
but less efficient execution-wise, because it involves an extra function call.

closes  #2303

IPython/parallel/error.py

@@ -1,335 +1,336 b''
 # encoding: utf-8
 
 """Classes and functions for kernel related errors and exceptions.
 
 Authors:
 
 * Brian Granger
 * Min RK
 """
 from __future__ import print_function
 
 import sys
 import traceback
 
 __docformat__ = "restructuredtext en"
 
 # Tell nose to skip this module
 __test__ = {}
 
 #-------------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-------------------------------------------------------------------------------
 
 #-------------------------------------------------------------------------------
 # Error classes
 #-------------------------------------------------------------------------------
 class IPythonError(Exception):
     """Base exception that all of our exceptions inherit from.
 
     This can be raised by code that doesn't have any more specific
     information."""
 
     pass
 
 # Exceptions associated with the controller objects
 class ControllerError(IPythonError): pass
 
 class ControllerCreationError(ControllerError): pass
 
 
 # Exceptions associated with the Engines
 class EngineError(IPythonError): pass
 
 class EngineCreationError(EngineError): pass
 
 class KernelError(IPythonError):
     pass
 
 class NotDefined(KernelError):
     def __init__(self, name):
         self.name = name
         self.args = (name,)
 
     def __repr__(self):
         return '<NotDefined: %s>' % self.name
 
     __str__ = __repr__
 
 
 class QueueCleared(KernelError):
     pass
 
 
 class IdInUse(KernelError):
     pass
 
 
 class ProtocolError(KernelError):
     pass
 
 
 class ConnectionError(KernelError):
     pass
 
 
 class InvalidEngineID(KernelError):
     pass
 
 
 class NoEnginesRegistered(KernelError):
     pass
 
 
 class InvalidClientID(KernelError):
     pass
 
 
 class InvalidDeferredID(KernelError):
     pass
 
 
 class SerializationError(KernelError):
     pass
 
 
 class MessageSizeError(KernelError):
     pass
 
 
 class PBMessageSizeError(MessageSizeError):
     pass
 
 
 class ResultNotCompleted(KernelError):
     pass
 
 
 class ResultAlreadyRetrieved(KernelError):
     pass
 
 class ClientError(KernelError):
     pass
 
 
 class TaskAborted(KernelError):
     pass
 
 
 class TaskTimeout(KernelError):
     pass
 
 
 class NotAPendingResult(KernelError):
     pass
 
 
 class UnpickleableException(KernelError):
     pass
 
 
 class AbortedPendingDeferredError(KernelError):
     pass
 
 
 class InvalidProperty(KernelError):
     pass
 
 
 class MissingBlockArgument(KernelError):
     pass
 
 
 class StopLocalExecution(KernelError):
     pass
 
 
 class SecurityError(KernelError):
     pass
 
 
 class FileTimeoutError(KernelError):
     pass
 
 class TimeoutError(KernelError):
     pass
 
 class UnmetDependency(KernelError):
     pass
 
 class ImpossibleDependency(UnmetDependency):
     pass
 
 class DependencyTimeout(ImpossibleDependency):
     pass
 
 class InvalidDependency(ImpossibleDependency):
     pass
 
 class RemoteError(KernelError):
     """Error raised elsewhere"""
     ename=None
     evalue=None
     traceback=None
     engine_info=None
 
     def __init__(self, ename, evalue, traceback, engine_info=None):
         self.ename=ename
         self.evalue=evalue
         self.traceback=traceback
         self.engine_info=engine_info or {}
         self.args=(ename, evalue)
 
     def __repr__(self):
         engineid = self.engine_info.get('engine_id', ' ')
         return "<Remote[%s]:%s(%s)>"%(engineid, self.ename, self.evalue)
 
     def __str__(self):
         return "%s(%s)" % (self.ename, self.evalue)
     
     def render_traceback(self):
         """render traceback to a list of lines"""
         return (self.traceback or "No traceback available").splitlines()
     
     # Special method for custom tracebacks within IPython
-    _render_traceback_ = render_traceback
-
+    def _render_traceback_(self):
+        return self.render_traceback()
+    
     def print_traceback(self, excid=None):
         """print my traceback"""
         print('\n'.join(self.render_traceback()))
 
     
 
 
 class TaskRejectError(KernelError):
     """Exception to raise when a task should be rejected by an engine.
 
     This exception can be used to allow a task running on an engine to test
     if the engine (or the user's namespace on the engine) has the needed
     task dependencies.  If not, the task should raise this exception.  For
     the task to be retried on another engine, the task should be created
     with the `retries` argument > 1.
 
     The advantage of this approach over our older properties system is that
     tasks have full access to the user's namespace on the engines and the
     properties don't have to be managed or tested by the controller.
     """
 
 
 class CompositeError(RemoteError):
     """Error for representing possibly multiple errors on engines"""
     def __init__(self, message, elist):
         Exception.__init__(self, *(message, elist))
         # Don't use pack_exception because it will conflict with the .message
         # attribute that is being deprecated in 2.6 and beyond.
         self.msg = message
         self.elist = elist
         self.args = [ e[0] for e in elist ]
 
     def _get_engine_str(self, ei):
         if not ei:
             return '[Engine Exception]'
         else:
             return '[%s:%s]: ' % (ei['engine_id'], ei['method'])
 
     def _get_traceback(self, ev):
         try:
             tb = ev._ipython_traceback_text
         except AttributeError:
             return 'No traceback available'
         else:
             return tb
 
     def __str__(self):
         s = str(self.msg)
         for en, ev, etb, ei in self.elist:
             engine_str = self._get_engine_str(ei)
             s = s + '\n' + engine_str + en + ': ' + str(ev)
         return s
 
     def __repr__(self):
         return "CompositeError(%i)"%len(self.elist)
     
     def render_traceback(self, excid=None):
         """render one or all of my tracebacks to a list of lines"""
         lines = []
         if excid is None:
             for (en,ev,etb,ei) in self.elist:
                 lines.append(self._get_engine_str(ei))
                 lines.extend((etb or 'No traceback available').splitlines())
                 lines.append('')
         else:
             try:
                 en,ev,etb,ei = self.elist[excid]
             except:
                 raise IndexError("an exception with index %i does not exist"%excid)
             else:
                 lines.append(self._get_engine_str(ei))
                 lines.extend((etb or 'No traceback available').splitlines())
         
         return lines
     
     def print_traceback(self, excid=None):
         print('\n'.join(self.render_traceback(excid)))
 
     def raise_exception(self, excid=0):
         try:
             en,ev,etb,ei = self.elist[excid]
         except:
             raise IndexError("an exception with index %i does not exist"%excid)
         else:
             raise RemoteError(en, ev, etb, ei)
 
 
 def collect_exceptions(rdict_or_list, method='unspecified'):
     """check a result dict for errors, and raise CompositeError if any exist.
     Passthrough otherwise."""
     elist = []
     if isinstance(rdict_or_list, dict):
         rlist = rdict_or_list.values()
     else:
         rlist = rdict_or_list
     for r in rlist:
         if isinstance(r, RemoteError):
             en, ev, etb, ei = r.ename, r.evalue, r.traceback, r.engine_info
             # Sometimes we could have CompositeError in our list.  Just take
             # the errors out of them and put them in our new list.  This
             # has the effect of flattening lists of CompositeErrors into one
             # CompositeError
             if en=='CompositeError':
                 for e in ev.elist:
                     elist.append(e)
             else:
                 elist.append((en, ev, etb, ei))
     if len(elist)==0:
         return rdict_or_list
     else:
         msg = "one or more exceptions from call to method: %s" % (method)
         # This silliness is needed so the debugger has access to the exception
         # instance (e in this case)
         try:
             raise CompositeError(msg, elist)
         except CompositeError as e:
             raise e
 
 def wrap_exception(engine_info={}):
     etype, evalue, tb = sys.exc_info()
     stb = traceback.format_exception(etype, evalue, tb)
     exc_content = {
         'status' : 'error',
         'traceback' : stb,
         'ename' : unicode(etype.__name__),
         'evalue' : unicode(evalue),
         'engine_info' : engine_info
     }
     return exc_content
 
 def unwrap_exception(content):
     err = RemoteError(content['ename'], content['evalue'],
                 ''.join(content['traceback']),
                 content.get('engine_info', {}))
     return err