practice.

Changeset c39f42f46a05 left a dangling head on 3.1.

specified network interface.

Patch contributed by Malte Swart. Addresses issue #17764.

HG :Enter commit message.  Lines beginning with 'HG:' are removed.

Close #18929: inspect.classify_class_attrs will now search the metaclasses (last) to find where an attr was defined.

Issue #18937: Add an assertLogs() context manager to unittest.TestCase to ensure that a block of code emits a message using the logging module.

This test will fail because a previous attempt to fix a merge error
in site.py was incorrect, but the test wasn't running so it wasn't
caught.  The next commit will fix the site.py bug.

It now always checks, instead of only when the LICENSE file doesn't exist.  It
is also protected by the 'network' resource, and uses a HEAD request since we
are only doing an existence check.