Rewrite syntax to be Python 3.5+

Used <https://github.com/asottile/pyupgrade/&gt;

IPython/utils/tests/test_openpy.py

@@ -17,10 +17,10 b' def test_read_file():'
         read_specified_enc = f.read()
     read_detected_enc = openpy.read_py_file(nonascii_path, skip_encoding_cookie=False)
     nt.assert_equal(read_detected_enc, read_specified_enc)
-    assert u'coding: iso-8859-5' in read_detected_enc
+    assert 'coding: iso-8859-5' in read_detected_enc
     
     read_strip_enc_cookie = openpy.read_py_file(nonascii_path, skip_encoding_cookie=True)
-    assert u'coding: iso-8859-5' not in read_strip_enc_cookie
+    assert 'coding: iso-8859-5' not in read_strip_enc_cookie
 
 def test_source_to_unicode():
     with io.open(nonascii_path, 'rb') as f:
@@ -29,4 +29,4 b' def test_source_to_unicode():'
                     source_bytes.decode('iso-8859-5').splitlines())
 
     source_no_cookie = openpy.source_to_unicode(source_bytes, skip_encoding_cookie=True)
-    nt.assert_not_in(u'coding: iso-8859-5', source_no_cookie)
+    nt.assert_not_in('coding: iso-8859-5', source_no_cookie)