blackbox.test_check fails in 2a format

Some blackbox check tests fail like this:

test: bzrlib.tests.blackbox.test_check.TestCheck.test_check_one_commit_tree
failure: bzrlib.tests.blackbox.test_check.TestCheck.test_check_one_commit_tree [
RemoteException: Traceback (most recent call last):
  File "/home/mbp/bzr/398668-2a-default/bzrlib/tests/blackbox/test_check.py", line 37, in test_check_one_commit_tree
    self.assertContainsRe(err, r"^Checking working tree at '.*'\.\n"
AssertionError: pattern "^Checking working tree at '.*'\.\nChecking repository at '.*'\.\nchecked repository.*\n 1
revisions\n 0 file-ids\n 0 unique file texts\n 0 repeated file texts\n 0 unreferenced text versions\nCh
ecking branch at '.*'\.\nchecked branch.*\n$" not found in
"""\
Checking working tree at 'file:///tmp/testbzr-4TD5P3.tmp/bzrlib.tests.blackbox.test_check.TestCheck.test_check_one_comm
it_tree/work/'.
Checking repository at 'file:///tmp/testbzr-4TD5P3.tmp/bzrlib.tests.blackbox.test_check.TestCheck.test_check_one_commit
_tree/work/'.
checked repository <bzrlib.transport.local.LocalTransport url=file:///tmp/testbzr-4TD5P3.tmp/bzrlib.tests.blackbox.test
_check.TestCheck.test_check_one_commit_tree/work/> format <RepositoryFormat2a>
     1 revisions
     1 file-ids
     0 unique file texts
     0 repeated file texts
     0 unreferenced text versions
Checking branch at 'file:///tmp/testbzr-4TD5P3.tmp/bzrlib.tests.blackbox.test_check.TestCheck.test_check_one_commit_tre
e/work/'.
checked branch file:///tmp/testbzr-4TD5P3.tmp/bzrlib.tests.blackbox.test_check.TestCheck.test_check_one_commit_tree/wor
k/ format Branch format 7
"""

]
test: bzrlib.tests.blackbox.test_check.TestCheck.test_check_repository
failure: bzrlib.tests.blackbox.test_check.TestCheck.test_check_repository [
RemoteException: Traceback (most recent call last):
  File "/home/mbp/bzr/398668-2a-default/bzrlib/tests/blackbox/test_check.py", line 59, in test_check_repository
    self.assertContainsRe(err, r"^Checking repository at '.*'\.\n"
AssertionError: pattern "^Checking repository at '.*'\.\nchecked repository.*\n 1 revisions\n 0 file-ids\n
0 unique file texts\n 0 repeated file texts\n 0 unreferenced text versions$" not found in
"""\
Checking repository at 'file:///tmp/testbzr-4TD5P3.tmp/bzrlib.tests.blackbox.test_check.TestCheck.test_check_repository
/work/'.
checked repository <bzrlib.transport.local.LocalTransport url=file:///tmp/testbzr-4TD5P3.tmp/bzrlib.tests.blackbox.test
_check.TestCheck.test_check_repository/work/> format <RepositoryFormat2a>
     1 revisions
     1 file-ids
     0 unique file texts
     0 repeated file texts
     0 unreferenced text versions
"""

It may be the problem is that they don't expect to see the root node.