Random failures on SFTPTransport tests on windows

[Martin Packman]

A number of SFTP tests have been randomly failing on babune over the past few months. All seem to involve PermissionError being thrown when trying to move a file. This is likely a race condition with the server or client not being careful about closing a shared file before allowing the other to continue.

Tracebacks are along the lines of:

<http://babune.ladeuil.net:24842/job/selftest-windows/224/testReport/junit/bzrlib.tests.per_transport/TransportTests/test_move_SFTPTransport_SFTPHomeDirServer_/>

Traceback (most recent call last):
  ...
  File "...\bzrlib\tests\per_transport.py", line 1001, in test_move
    t.move('c', 'b')
  File "...\bzrlib\transport\sftp.py", line 773, in move
    self._rename_and_overwrite(path_from, path_to)
  File "...\bzrlib\transport\sftp.py", line 767, in _rename_and_overwrite
    ': unable to rename to %r' % (abs_to))
  File "...\bzrlib\transport\sftp.py", line 706, in _translate_io_exception
    self._translate_error(e, path, raise_generic=False)
  File "...\bzrlib\transport\__init__.py", line 316, in _translate_error
    raise errors.PermissionDenied(path, extra=e)
PermissionDenied: Permission denied: "c": [Errno 13] Permission denied

<http://babune.ladeuil.net:24842/job/selftest-windows/224/testReport/bzrlib.tests.per_transport/TransportTests/test_put_file_SFTPTransport_SFTPSiblingAbsoluteServer_/>

Traceback (most recent call last):
  ...
  File "...\bzrlib\tests\per_transport.py", line 403, in test_put_file
    result = t.put_file('a', StringIO('new\ncontents for\na\n'))
  File "...\bzrlib\transport\sftp.py", line 495, in put_file
    return self._put(final_path, f, mode=mode)
  File "...\bzrlib\transport\sftp.py", line 526, in _put
    self._rename_and_overwrite(tmp_abspath, abspath)
  File "...\bzrlib\transport\sftp.py", line 767, in _rename_and_overwrite
    ': unable to rename to %r' % (abs_to))
  File "...\bzrlib\transport\sftp.py", line 706, in _translate_io_exception
    self._translate_error(e, path, raise_generic=False)
  File "...\bzrlib\transport\__init__.py", line 316, in _translate_error
    raise errors.PermissionDenied(path, extra=e)
PermissionDenied: Permission denied: "/C:/windows/temp/testbzr-fqqbul.tmp/ort_SFTPSiblingAbsoluteServer)/work/a.tmp.1289089305.118000000.384.399958340": [Errno 13] Permission denied

[Vincent Ladeuil (vila)]

There is a quite suspicious:

class TransportTests(TestTransportImplementation):

    def setUp(self):
        super(TransportTests, self).setUp()
        self._captureVar('BZR_NO_SMART_VFS', None)

    def check_transport_contents(self, content, transport, relpath):
        """Check that transport.get(relpath).read() == content."""
        self.assertEqualDiff(content, transport.get(relpath).read())

We'd better use get_bytes() there instead of get()...