Issue #16714: use 'raise' exceptions, don't 'throw'.

Patch by Serhiy Storchaka.
diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index 7017e9f..6257936 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -447,10 +447,10 @@
 
 
     def assertRaises(self, excClass, callableObj=None, *args, **kwargs):
-        """Fail unless an exception of class excClass is thrown
+        """Fail unless an exception of class excClass is raised
            by callableObj when invoked with arguments args and keyword
            arguments kwargs. If a different type of exception is
-           thrown, it will not be caught, and the test case will be
+           raised, it will not be caught, and the test case will be
            deemed to have suffered an error, exactly as for an
            unexpected exception.