The tmp test dir associated with the following tests, isn't removed when the test ends:
bzrlib.tests.blackbox.test_too_much.HTTPTests.test_branch
bzrlib.tests.per_transport.TransportTests.test_has(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.blackbox.test_dump_btree.TestDumpBtree.test_dump_btree_http_smoke
bzrlib.tests.per_branch.test_branch.ChrootedTests.test_open_containing(BzrBranchFormat7)
bzrlib.tests.per_branch.test_branch.ChrootedTests.test_open_containing(BzrBranchFormat8)
bzrlib.tests.per_branch.test_branch.ChrootedTests.test_open_containing(BzrBranchFormat4)
bzrlib.tests.per_branch.test_branch.ChrootedTests.test_open_containing(RemoteBranchFormat-default)
bzrlib.tests.per_branch.test_branch.ChrootedTests.test_open_containing(RemoteBranchFormat-v2)
bzrlib.tests.per_transport.TransportTests.test_clone(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_copy_to(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_get(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_get_bytes(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_readv(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_readv_out_of_order(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_readv_short_read(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_readv_with_adjust_for_latency(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_readv_with_adjust_for_latency_with_big_file(HttpTransport_urllib,HttpServer_urllib)
bzrlib.tests.per_transport.TransportTests.test_unicode_paths(HttpTransport_urllib,HttpServer_urllib)
This means that they keep some file open (or something like that) which prevents windows deleting them (or their containing directory).
The leak fixes appear to have resolved this problem