Remove the __unicode__ method from exceptions.  Allows unicode() to be called
on exception classes.  Would require introducing a tp_unicode slot to make it
work otherwise.

Fixes bug #1551432 and will be backported.
diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index af07aa8..27d88a0 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -304,6 +304,15 @@
                 return -1
         self.assertRaises(RuntimeError, g)
 
+    def testUnicodeStrUsage(self):
+        # Make sure both instances and classes have a str and unicode
+        # representation.
+        self.failUnless(str(Exception))
+        self.failUnless(unicode(Exception))
+        self.failUnless(str(Exception('a')))
+        self.failUnless(unicode(Exception(u'a')))
+
+
 def test_main():
     run_unittest(ExceptionTests)