More Python 3 compatibility fixes in core.

IPython/core/formatters.py

@@ -29,6 +29,7 b' from StringIO import StringIO'
 from IPython.config.configurable import Configurable
 from IPython.lib import pretty
 from IPython.utils.traitlets import Bool, Dict, Int, Unicode, CUnicode, ObjectName
+from IPython.utils.py3compat import unicode_to_str
 
 
 #-----------------------------------------------------------------------------
@@ -439,7 +440,7 b' class PlainTextFormatter(BaseFormatter):'
             # ensure that stream does not get a mix of unicode and bytestrings,
             # or it will cause trouble.
             printer = pretty.RepresentationPrinter(stream, self.verbose,
-                self.max_width, self.newline.encode(),
+                self.max_width, unicode_to_str(self.newline),
                 singleton_pprinters=self.singleton_printers,
                 type_pprinters=self.type_printers,
                 deferred_pprinters=self.deferred_printers)

IPython/core/inputsplitter.py

@@ -75,6 +75,7 b' from StringIO import StringIO'
 
 # IPython modules
 from IPython.utils.text import make_quoted_expr
+from IPython.utils.py3compat import cast_unicode
 
 #-----------------------------------------------------------------------------
 # Globals
@@ -837,8 +838,7 b' class IPythonInputSplitter(InputSplitter):'
             return super(IPythonInputSplitter, self).push(lines)
 
         # We must ensure all input is pure unicode
-        if type(lines)==str:
-            lines = lines.decode(self.encoding)
+        lines = cast_unicode(lines, self.encoding)
 
         lines_list = lines.splitlines()