don't add unicode paths to sys.path

on Python 2

causes unicode warnings comparing unicode to str when non-ascii

IPython/core/application.py

@@ -211,9 +211,15 b' class BaseIPythonApplication(Application):'
             return crashhandler.crash_handler_lite(etype, evalue, tb)
     
     def _ipython_dir_changed(self, name, old, new):
-        if old in sys.path:
-            sys.path.remove(old)
-        sys.path.append(os.path.abspath(new))
+        str_old = py3compat.cast_bytes_py2(os.path.abspath(old),
+            sys.getfilesystemencoding()
+        )
+        if str_old in sys.path:
+            sys.path.remove(str_old)
+        str_path = py3compat.cast_bytes_py2(os.path.abspath(new),
+            sys.getfilesystemencoding()
+        )
+        sys.path.append(str_path)
         if not os.path.isdir(new):
             os.makedirs(new, mode=0o777)
         readme = os.path.join(new, 'README')

IPython/utils/syspathcontext.py

@@ -20,6 +20,8 b' Authors:'
 
 import sys
 
+from IPython.utils.py3compat import cast_bytes_py2
+
 #-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
@@ -28,7 +30,7 b' class appended_to_syspath(object):'
     """A context for appending a directory to sys.path for a second."""
 
     def __init__(self, dir):
-        self.dir = dir
+        self.dir = cast_bytes_py2(dir, sys.getdefaultencoding())
 
     def __enter__(self):
         if self.dir not in sys.path:
@@ -50,7 +52,7 b' class prepended_to_syspath(object):'
     """A context for prepending a directory to sys.path for a second."""
 
     def __init__(self, dir):
-        self.dir = dir
+        self.dir = cast_bytes_py2(dir, sys.getdefaultencoding())
 
     def __enter__(self):
         if self.dir not in sys.path: