Only the parts which are relevant for 3.x branch.

Merged revisions 78757-78758,78769,78815 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

........
  r78757 | florent.xicluna | 2010-03-07 13:14:25 +0100 (dim, 07 mar 2010) | 2 lines

  Fix some py3k warnings in the standard library.
........
  r78758 | florent.xicluna | 2010-03-07 13:18:33 +0100 (dim, 07 mar 2010) | 4 lines

  Issue #7849: Now the utility ``check_warnings`` verifies if the warnings are
  effectively raised.  A new utility ``check_py3k_warnings`` deals with py3k warnings.
........
  r78769 | florent.xicluna | 2010-03-07 20:14:12 +0100 (dim, 07 mar 2010) | 2 lines

  Refresh the documentation for the test.test_support module.
........
  r78815 | florent.xicluna | 2010-03-09 20:57:01 +0100 (mar, 09 mar 2010) | 2 lines

  #7772: Fix test_py3kwarn. Now the test suite could pass with "-3" flag.
........

Lib/test/support.py

@@ -16,6 +16,7 @@ import warnings
 import unittest
 import importlib
 import collections
+import re
 
 __all__ = ["Error", "TestFailed", "ResourceDenied", "import_module",
            "verbose", "use_resources", "max_memuse", "record_original_stdout",
@@ -464,22 +465,80 @@ class WarningsRecorder(object):
        entry to the warnings.catch_warnings() context manager.
     """
     def __init__(self, warnings_list):
-        self.warnings = warnings_list
+        self._warnings = warnings_list
+        self._last = 0
 
     def __getattr__(self, attr):
-        if self.warnings:
-            return getattr(self.warnings[-1], attr)
+        if len(self._warnings) > self._last:
+            return getattr(self._warnings[-1], attr)
         elif attr in warnings.WarningMessage._WARNING_DETAILS:
             return None
         raise AttributeError("%r has no attribute %r" % (self, attr))
 
+    @property
+    def warnings(self):
+        return self._warnings[self._last:]
+
     def reset(self):
-        del self.warnings[:]
+        self._last = len(self._warnings)
+
+
+def _filterwarnings(filters, quiet=False):
+    """Catch the warnings, then check if all the expected
+    warnings have been raised and re-raise unexpected warnings.
+    If 'quiet' is True, only re-raise the unexpected warnings.
+    """
+    # Clear the warning registry of the calling module
+    # in order to re-raise the warnings.
+    frame = sys._getframe(2)
+    registry = frame.f_globals.get('__warningregistry__')
+    if registry:
+        registry.clear()
+    with warnings.catch_warnings(record=True) as w:
+        # Set filter "always" to record all warnings.  Because
+        # test_warnings swap the module, we need to look up in
+        # the sys.modules dictionary.
+        sys.modules['warnings'].simplefilter("always")
+        yield WarningsRecorder(w)
+    # Filter the recorded warnings
+    reraise = [warning.message for warning in w]
+    missing = []
+    for msg, cat in filters:
+        seen = False
+        for exc in reraise[:]:
+            message = str(exc)
+            # Filter out the matching messages
+            if (re.match(msg, message, re.I) and
+                issubclass(exc.__class__, cat)):
+                seen = True
+                reraise.remove(exc)
+        if not seen and not quiet:
+            # This filter caught nothing
+            missing.append((msg, cat.__name__))
+    if reraise:
+        raise AssertionError("unhandled warning %r" % reraise[0])
+    if missing:
+        raise AssertionError("filter (%r, %s) did not catch any warning" %
+                             missing[0])
+
 
 @contextlib.contextmanager
-def check_warnings():
-    with warnings.catch_warnings(record=True) as w:
-        yield WarningsRecorder(w)
+def check_warnings(*filters, **kwargs):
+    """Context manager to silence warnings.
+
+    Accept 2-tuples as positional arguments:
+        ("message regexp", WarningCategory)
+
+    Optional argument:
+     - if 'quiet' is True, it does not fail if a filter catches nothing
+        (default False)
+
+    Without argument, it defaults to:
+        check_warnings(("", Warning), quiet=False)
+    """
+    if not filters:
+        filters = (("", Warning),)
+    return _filterwarnings(filters, kwargs.get('quiet'))
 
 
 class CleanImport(object):
@@ -714,7 +773,6 @@ _4G = 4 * _1G
 MAX_Py_ssize_t = sys.maxsize
 
 def set_memlimit(limit):
-    import re
     global max_memuse
     global real_max_memuse
     sizes = {