Backport PR #2500: Add `encoding` attribute to `OutStream` class.

This means that `sys.stdout.encoding` returns something useful instead of raising an AttributeError.

Closes  #2220.

IPython/zmq/iostream.py

@@ -1,91 +1,91 b''
 import sys
 import time
 from io import StringIO
 
 from session import extract_header, Message
 
-from IPython.utils import io, text, encoding
+from IPython.utils import io, text
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Stream classes
 #-----------------------------------------------------------------------------
 
 class OutStream(object):
     """A file like object that publishes the stream to a 0MQ PUB socket."""
 
     # The time interval between automatic flushes, in seconds.
     flush_interval = 0.05
     topic=None
 
     def __init__(self, session, pub_socket, name):
+        self.encoding = 'UTF-8'
         self.session = session
         self.pub_socket = pub_socket
         self.name = name
         self.parent_header = {}
         self._new_buffer()
 
     def set_parent(self, parent):
         self.parent_header = extract_header(parent)
 
     def close(self):
         self.pub_socket = None
 
     def flush(self):
         #io.rprint('>>>flushing output buffer: %s<<<' % self.name)  # dbg
         if self.pub_socket is None:
             raise ValueError(u'I/O operation on closed file')
         else:
             data = self._buffer.getvalue()
             if data:
                 content = {u'name':self.name, u'data':data}
                 msg = self.session.send(self.pub_socket, u'stream', content=content,
                                        parent=self.parent_header, ident=self.topic)
 
                 if hasattr(self.pub_socket, 'flush'):
                     # socket itself has flush (presumably ZMQStream)
                     self.pub_socket.flush()
                 self._buffer.close()
                 self._new_buffer()
 
     def isatty(self):
         return False
 
     def next(self):
         raise IOError('Read not supported on a write only stream.')
 
     def read(self, size=-1):
         raise IOError('Read not supported on a write only stream.')
 
     def readline(self, size=-1):
         raise IOError('Read not supported on a write only stream.')
 
     def write(self, string):
         if self.pub_socket is None:
             raise ValueError('I/O operation on closed file')
         else:
             # Make sure that we're handling unicode
             if not isinstance(string, unicode):
-                enc = encoding.DEFAULT_ENCODING
-                string = string.decode(enc, 'replace')
-            
+                string = string.decode(self.encoding, 'replace')
+
             self._buffer.write(string)
             current_time = time.time()
             if self._start <= 0:
                 self._start = current_time
             elif current_time - self._start > self.flush_interval:
                 self.flush()
 
     def writelines(self, sequence):
         if self.pub_socket is None:
             raise ValueError('I/O operation on closed file')
         else:
             for string in sequence:
                 self.write(string)
 
     def _new_buffer(self):
         self._buffer = StringIO()
         self._start = -1