TST: remove assert messages (#790)

remove ambiguous assert messages for unicode_literals test

IPython/core/tests/test_interactiveshell.py

@@ -139,10 +139,10 b' class InteractiveShellTestCase(unittest.TestCase):'
         ip = get_ipython()
         try:
             ip.run_cell(u'byte_str = "a"')
-            assert isinstance(ip.user_ns['byte_str'], str), 'string literals are byte strings by default'
+            assert isinstance(ip.user_ns['byte_str'], str) # string literals are byte strings by default
             ip.run_cell('from __future__ import unicode_literals')
             ip.run_cell(u'unicode_str = "a"')
-            assert isinstance(ip.user_ns['unicode_str'], unicode), 'strings literals are now unicode'
+            assert isinstance(ip.user_ns['unicode_str'], unicode) # strings literals are now unicode
         finally:
             # Reset compiler flags so we don't mess up other tests.
             ip.compile.reset_compiler_flags()