"Failed to load compiled extensions" warning breaks the test suite

Caught by the test botnet.

We support running without extensions anyway so the test suite should pass without them.

per_repository.test_repository.TestRepository.test_clone_to_hpss(RepositoryFormatCHK1) OK 0ms
/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:
    No module named _chunks_to_lines_pyx
    cannot import name _btree_serializer_pyx
    No module named _rio_pyx
    No module named _dirstate_helpers_pyx
    No module named _known_graph_pyx
    No module named _bencode_pyx
    No module named _chk_map_pyx
    No module named _annotator_pyx
    No module named _knit_load_data_pyx
    No module named _groupcompress_pyx
    Bazaar can run, but performance may be reduced.
    Check Bazaar is correctly installed or set ignore_missing_extensions
  % '\n '.join(_extension_load_failures,))

======================================================================
FAIL: bzrlib.tests.blackbox.test_cat.TestCat.test_cat_different_id (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_cat.py", line 103, in test_cat_different_id
    self.assertEqual('', err)
AssertionError: not equal:
a = ''
b = "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _rio_pyx\n No module named _dirstate_helpers_pyx\n No module named _chk_map_pyx\n No module named _bencode_pyx\n No module named _known_graph_pyx\n No module named _annotator_pyx\n No module named _knit_load_data_pyx\n No module named _groupcompress_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.blackbox.test_diff.TestExternalDiff.test_external_diff (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_diff.py", line 370, in test_external_diff
    self.assertEqual('', err)
AssertionError: not equal:
a = ''
b = "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _rio_pyx\n No module named _dirstate_helpers_pyx\n No module named _chk_map_pyx\n No module named _bencode_pyx\n No module named _known_graph_pyx\n No module named _annotator_pyx\n No module named _knit_load_data_pyx\n No module named _groupcompress_pyx\n No module named _readdir_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.blackbox.test_locale.TestLocale.test_log_C (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_locale.py", line 48, in test_log_C
    self.assertEqual('', err)
AssertionError: not equal:
a = ''
b = "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _rio_pyx\n No module named _dirstate_helpers_pyx\n No module named _chk_map_pyx\n No module named _bencode_pyx\n No module named _known_graph_pyx\n No module named _annotator_pyx\n No module named _knit_load_data_pyx\n No module named _groupcompress_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.blackbox.test_serve.TestBzrServe.test_bzr_serve_inet_readonly (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 114, in test_bzr_serve_inet_readonly
    self.assertInetServerShutsdownCleanly(process)
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 54, in assertInetServerShutsdownCleanly
    self.assertEqual('', result[1])
AssertionError: not equal:
a = ''
b = "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _bencode_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.blackbox.test_serve.TestBzrServe.test_bzr_serve_inet_readwrite (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 125, in test_bzr_serve_inet_readwrite
    self.assertInetServerShutsdownCleanly(process)
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 54, in assertInetServerShutsdownCleanly
    self.assertEqual('', result[1])
AssertionError: not equal:
a = ''
b = "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _bencode_pyx\n No module named _chk_map_pyx\n No module named _known_graph_pyx\n No module named _annotator_pyx\n No module named _knit_load_data_pyx\n No module named _groupcompress_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.blackbox.test_serve.TestBzrServe.test_bzr_serve_port_readonly (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 132, in test_bzr_serve_port_readonly
    self.assertServerFinishesCleanly(process)
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 62, in assertServerFinishesCleanly
    self.assertEqual('bzr: interrupted\n', result[1])
AssertionError: not equal:
a = 'bzr: interrupted\n'
b = "bzr: interrupted\n/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _bencode_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.blackbox.test_serve.TestBzrServe.test_bzr_serve_port_readwrite (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 143, in test_bzr_serve_port_readwrite
    self.assertServerFinishesCleanly(process)
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 62, in assertServerFinishesCleanly
    self.assertEqual('bzr: interrupted\n', result[1])
AssertionError: not equal:
a = 'bzr: interrupted\n'
b = "bzr: interrupted\n/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _bencode_pyx\n No module named _chk_map_pyx\n No module named _known_graph_pyx\n No module named _annotator_pyx\n No module named _knit_load_data_pyx\n No module named _groupcompress_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.blackbox.test_serve.TestBzrServe.test_bzr_serve_supports_protocol (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 155, in test_bzr_serve_supports_protocol
    self.assertServerFinishesCleanly(process)
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/blackbox/test_serve.py", line 62, in assertServerFinishesCleanly
    self.assertEqual('bzr: interrupted\n', result[1])
AssertionError: not equal:
a = 'bzr: interrupted\n'
b = "bzr: interrupted\n/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n No module named _bencode_pyx\n No module named _chk_map_pyx\n No module named _known_graph_pyx\n No module named _annotator_pyx\n No module named _knit_load_data_pyx\n No module named _groupcompress_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"

======================================================================
FAIL: bzrlib.tests.test_selftest.TestActuallyStartBzrSubprocess.test_start_and_stop_bzr_subprocess_send_signal (subunit.RemotedTestCase)
----------------------------------------------------------------------
RemoteException: Traceback (most recent call last):
  File "/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/tests/test_selftest.py", line 2378, in test_start_and_stop_bzr_subprocess_send_signal
    self.assertEqual('bzr: interrupted\n', result[1])
AssertionError: not equal:
a = 'bzr: interrupted\n'
b = "bzr: interrupted\n/Users/vila/buildbot/bzr/slaves/leopard/tests/leopard/build/bzrlib/osutils.py:928: UserWarning: bzr: warning: Failed to load compiled extensions:\n No module named _chunks_to_lines_pyx\n cannot import name _btree_serializer_pyx\n Bazaar can run, but performance may be reduced.\n Check Bazaar is correctly installed or set ignore_missing_extensions\n % '\\n '.join(_extension_load_failures,))\n"