merge 3.2 (#12544)

diff --cc Lib/unittest/case.py
index 5b7c29dd2688e1c00e7dd2dcdc1f719785a1c848,3133907e4a9a39cbbc65bc7ff6bd137a0de5ca86..d82fa2092715ced37974390dcee59330dec72ed5
--- 1/Lib/unittest/case.py
--- 2/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@@ -209,36 -192,16 +209,15 @@@ class _AssertWarnsContext(_AssertRaises
              return
          # Now we simply try to choose a helpful failure message
          if first_matching is not None:
 -            raise self.failureException('"%s" does not match "%s"' %
 -                     (self.expected_regex.pattern, str(first_matching)))
 +            self._raiseFailure('"{}" does not match "{}"'.format(
 +                     self.expected_regex.pattern, str(first_matching)))
          if self.obj_name:
 -            raise self.failureException("{0} not triggered by {1}"
 -                .format(exc_name, self.obj_name))
 +            self._raiseFailure("{} not triggered by {}".format(exc_name,
 +                                                               self.obj_name))
          else:
 -            raise self.failureException("{0} not triggered"
 -                .format(exc_name))
 +            self._raiseFailure("{} not triggered".format(exc_name))
  
  
- class _TypeEqualityDict(object):
- 
-     def __init__(self, testcase):
-         self.testcase = testcase
-         self._store = {}
- 
-     def __setitem__(self, key, value):
-         self._store[key] = value
- 
-     def __getitem__(self, key):
-         value = self._store[key]
-         if isinstance(value, str):
-             return getattr(self.testcase, value)
-         return value
- 
-     def get(self, key, default=None):
-         if key in self._store:
-             return self[key]
-         return default
- 
- 
  class TestCase(object):
      """A class whose instances are single test cases.