Read Until discards read data on failed test

[EdwinFairchild]

I am using Read Until extensively in my testing, however on failed tests I do not have any way of knowing what the serial output was. All I know is that it did not find what it was expecting. For some cases seeing what was sent during a failed test can greatly help debug.

Python not being my forte, I have been trying to implement something with the same functionality as Read Until but have it also return the data.
I have had no luck. Can you provide some insight as to how you would accomplish this?

[EdwinFairchild]

Best I could do was this Expect And Timeout keyword which passes the NONE parameter in place of a delimiter which according do the code causes Read Until to read until a LF is received. At which point I log that data and then check if it contains my expected string.

Expect And Timeout
    [Arguments]    ${data}    ${timeout}    ${port}    
    [Timeout]    ${timeout}
    ${EMPTY}=    Set Variable    ""
    Log To Console    \n
    WHILE    True    limit=500000
        ${source}=    Read Until   NONE    NONE    NONE    ${port}
        Log To Console    ${source}
        ${contains}=    Run Keyword And Return Status    Should Contain    ${source}    ${data}
        IF    ${contains}
            Pass Execution    ------------------------------------------------------------------------------
        END
    END
    Fail    "Test Failed"