cleaner string/bytes solution, closes #4759

Thanks @takluyver for the suggestion. I'll eventually learn this
strings/bytes/unicode stuff properly for Python3.

IPython/terminal/tests/test_embed.py

@@ -20,7 +20,7 b' from IPython.utils.tempdir import NamedFileInTemporaryDirectory'
 # Tests
 #-----------------------------------------------------------------------------
 
-_sample_embed = """
+_sample_embed = b"""
 from __future__ import print_function
 import IPython
 
@@ -33,12 +33,12 b' IPython.embed()'
 print('bye!')
 """
 
-_exit = "exit\r".encode('UTF-8')
+_exit = b"exit\r"
 
 def test_ipython_embed():
     """test that `IPython.embed()` works"""
     with NamedFileInTemporaryDirectory('file_with_embed.py') as f:
-        f.write(_sample_embed.encode('UTF-8'))
+        f.write(_sample_embed)
         f.flush()
 
         # run `python file_with_embed.py`