Further Python 3 fixes in core.

IPython/core/interactiveshell.py

@@ -1677,7 +1677,9 b' class InteractiveShell(SingletonConfigurable, Magic):'
 
             # Remove some chars from the delimiters list.  If we encounter
             # unicode chars, discard them.
-            delims = readline.get_completer_delims().encode("ascii", "ignore")
+            delims = readline.get_completer_delims()
+            if not py3compat.PY3:
+                delims = delims.encode("ascii", "ignore")
             for d in self.readline_remove_delims:
                 delims = delims.replace(d, "")
             delims = delims.replace(ESC_MAGIC, '')

IPython/core/macro.py

@@ -10,6 +10,8 b''
 import re
 import sys
 
+from IPython.utils import py3compat
+
 coding_declaration = re.compile(r"#\s*coding[:=]\s*([-\w.]+)")
 
 class Macro(object):
@@ -37,8 +39,7 b' class Macro(object):'
         self.value = code + '\n'
     
     def __str__(self):
-        enc = sys.stdin.encoding or sys.getdefaultencoding()
-        return self.value.encode(enc, "replace")
+        return py3compat.unicode_to_str(self.value)
     
     def __unicode__(self):
         return self.value

IPython/core/magic.py

@@ -676,7 +676,7 b' Currently the magic system has the following functions:\\n"""'
        
         %psearch -a _*         list objects beginning with a single underscore"""
         try:
-            parameter_s = parameter_s.encode('ascii')
+            parameter_s.encode('ascii')
         except UnicodeEncodeError:
             print 'Python identifiers can only contain ascii characters.'
             return