Deprecate bsddb for removal in Python 3.0.

Closes issue 3776.
Review by Nick Coghlan.
diff --git a/Lib/bsddb/__init__.py b/Lib/bsddb/__init__.py
index 0e5169c..0af679f 100644
--- a/Lib/bsddb/__init__.py
+++ b/Lib/bsddb/__init__.py
@@ -42,6 +42,12 @@
 import sys
 absolute_import = (sys.version_info[0] >= 3)
 
+if sys.py3kwarning:
+    import warnings
+    warnings.warnpy3k("in 3.x, bsddb has been removed; "
+                      "please use the pybsddb project instead",
+                      DeprecationWarning, 2)
+
 try:
     if __name__ == 'bsddb3':
         # import _pybsddb binary as it should be the more recent version from
diff --git a/Lib/dbhash.py b/Lib/dbhash.py
index 9f8a9c3..5ca0bc1 100644
--- a/Lib/dbhash.py
+++ b/Lib/dbhash.py
@@ -1,6 +1,9 @@
 """Provide a (g)dbm-compatible interface to bsddb.hashopen."""
 
 import sys
+if sys.py3kwarning:
+    import warnings
+    warnings.warnpy3k("in 3.x, dbhash has been removed", DeprecationWarning, 2)
 try:
     import bsddb
 except ImportError:
diff --git a/Lib/test/test_py3kwarn.py b/Lib/test/test_py3kwarn.py
index 7bfe1e5..780de74 100644
--- a/Lib/test/test_py3kwarn.py
+++ b/Lib/test/test_py3kwarn.py
@@ -305,7 +305,7 @@
                            'sunos5' : ('sunaudiodev', 'SUNAUDIODEV'),
                           }
     optional_modules = ('bsddb185', 'Canvas', 'dl', 'linuxaudiodev', 'imageop',
-                        'sv', 'cPickle')
+                        'sv', 'cPickle', 'bsddb', 'dbhash')
 
     def check_removal(self, module_name, optional=False):
         """Make sure the specified module, when imported, raises a
diff --git a/Lib/test/test_warnings.py b/Lib/test/test_warnings.py
index 1520bf2..9980f24 100644
--- a/Lib/test/test_warnings.py
+++ b/Lib/test/test_warnings.py
@@ -508,6 +508,7 @@
         wmod = self.module
         with wmod.catch_warnings(module=wmod, record=True) as w:
             self.assertEqual(w, [])
+            self.assertRaises(AttributeError, getattr, w, 'message')
             wmod.simplefilter("always")
             wmod.warn("foo")
             self.assertEqual(str(w.message), "foo")
diff --git a/Lib/warnings.py b/Lib/warnings.py
index b699c43..9ec04be 100644
--- a/Lib/warnings.py
+++ b/Lib/warnings.py
@@ -314,7 +314,14 @@
         self.append(WarningMessage(*args, **kwargs))
 
     def __getattr__(self, attr):
-        return getattr(self[-1], attr)
+        """Return attributes from the last caught warning, or raise
+        AttributeError."""
+        try:
+            return getattr(self[-1], attr)
+        except IndexError:
+            raise AttributeError("no recorded warning to read "
+                                    "{0!r} attribute from".format(attr))
+
 
     def reset(self):
         del self[:]