In the past (<= 2.6) regrtest skipped a test if any import failure
happened, which masked various real test failures.  This was fixed, and
tests that should be skipped if certain modules are not available were
changed to use (test_)support.import_module, which causes a skip if that
particular module cannot be imported.

If python is compiled --without-threads, then the following tests
currently 'crash' because they cannot import thread and/or threading:

    test_hashlib test_asyncore test_wait3 test_threading test_socket
    test_wait4 test_capi test_xmlrpc test_ctypes
    test_zipimport_support test_threading_local test_multiprocessing
    test_file2k test_smtplib test_threadedtempfile test_threadsignals
    test_thread test_queue test_asynchat test_contextlib
    test_bz2 test_ftplib test_cmd test_pdb test_io test_doctest
    test_sqlite test_logging test_telnetlib test_threaded_import
    test_httpservers test_fork1 test_docxmlrpc test_urllib2_localnet
    test_poplib test_socketserver

All of these tests should either be changed to use import_module when
importing thread/threading, or changed so that the tests requiring
thread support are skipped if thread support is not available.

Note that test_bsddb3 also fails, but it is not an import error crash.