linux shell prompt not found

I'm having problems getting linux shell prompt to match in ShellDriver. This is what have this in config yaml

      - ShellDriver:
#          prompt: 'root@\w+:[^ ]+ '
          prompt: 'root@BeaglePlay'
          login_prompt: ' login: '
          username: 'root'

The default shell prompt on this platform is root@BeaglePlay:~# and the initial prompt (copied from the labgrid docs) didn't work, so I tried a more basic match without the regex and it still doesn't match. What am I doing wrong here?

In the backtrace below, you can see exactly what's in the pexpect buffer (including the $MARKER) and the re.compile expression, but I can't figure out why this isn't matching.

<labgrid.util.expect.PtxExpect object at 0x7f4581da2750>
command: None
args: None
buffer (last 100 chars): b"T'\r\n\x1b[?2004hroot@BeaglePlay:~# echo 'MMNW''MJJJKT'\r\n\x1b[?2004l\rMMNWMJJJKT\r\n\x1b[?2004hroot@BeaglePlay:~# "
before (last 100 chars): b"T'\r\n\x1b[?2004hroot@BeaglePlay:~# echo 'MMNW''MJJJKT'\r\n\x1b[?2004l\rMMNWMJJJKT\r\n\x1b[?2004hroot@BeaglePlay:~# "
after: <class 'pexpect.exceptions.TIMEOUT'>
match: None
match_index: None
exitstatus: None
pid: None
child_fd: -1
closed: True
timeout: 30
delimiter: <class 'pexpect.exceptions.EOF'>
logfile: None
logfile_read: None
logfile_send: None
maxread: 1
ignorecase: False
searchwindowsize: None
delaybeforesend: 0.05
delayafterclose: 0.1
delayafterterminate: 0.1
searcher: searcher_re:
    0: re.compile(b'MMNWMJJJKT\\s+root@BeaglePlay')

Start at the ShellDriver prompt-matching entry point and compare the configured prompt with the pexpect buffer and compiled expression shown in the report. Done means the configured Linux shell prompt is recognized on this platform without the timeout, with the behavior covered by the relevant existing test entry point if one is identified.