remove the function unicode_to_str as in python3 it has become redundant

IPython/core/interactiveshell.py

@@ -2202,14 +2202,12 b' class InteractiveShell(SingletonConfigurable):'
             with AvoidUNCPath() as path:
                 if path is not None:
                     cmd = '"pushd %s &&"%s' % (path, cmd)
-                cmd = py3compat.unicode_to_str(cmd)
                 try:
                     ec = os.system(cmd)
                 except KeyboardInterrupt:
                     print('\n' + self.get_exception_only(), file=sys.stderr)
                     ec = -2
         else:
-            cmd = py3compat.unicode_to_str(cmd)
             # For posix the result of the subprocess.call() below is an exit
             # code, which by convention is zero for success, positive for
             # program failure.  Exit codes above 128 are reserved for signals,

IPython/core/macro.py

@@ -37,7 +37,7 b' class Macro(object):'
         self.value = code + '\n'
     
     def __str__(self):
-        return py3compat.unicode_to_str(self.value)
+        return self.value
     
     def __unicode__(self):
         return self.value

IPython/core/tests/test_application.py

@@ -42,7 +42,7 b' def test_unicode_ipdir():'
     
     old_ipdir1 = os.environ.pop("IPYTHONDIR", None)
     old_ipdir2 = os.environ.pop("IPYTHON_DIR", None)
-    os.environ["IPYTHONDIR"] = py3compat.unicode_to_str(ipdir, "utf-8")
+    os.environ["IPYTHONDIR"] = ipdir
     try:
         app = BaseIPythonApplication()
         # The lines below are copied from Application.initialize()

IPython/utils/path.py

@@ -87,7 +87,7 b" def unquote_filename(name, win32=(sys.platform=='win32')):"
 def compress_user(path):
     """Reverse of :func:`os.path.expanduser`
     """
-    path = py3compat.unicode_to_str(path, sys.getfilesystemencoding())
+    path = str(path)
     home = os.path.expanduser('~')
     if path.startswith(home):
         path =  "~" + path[len(home):]