Invoking `mergemaster` fails with the error message `Unknown modifier 't'`. Error messages of such low quality should not be shown to the user. He_she needs to know what went wrong (in which file, etc.) and how to get starting fixing the issue. The complete output of the failing command is:

    # mergemaster

    *** The directory specified for the temporary root environment,
        /var/tmp/temproot, exists.  This can be a security risk if untrusted
        users have access to the system.

      Use 'd' to delete the old /var/tmp/temproot and continue
      Use 't' to select a new temporary root directory
      Use 'e' to exit mergemaster

      Default is to use /var/tmp/temproot as is

    How should I deal with this? [Use the existing /var/tmp/temproot] 

       *** Leaving /var/tmp/temproot intact

    *** Creating the temporary root environment in /var/tmp/temproot
     *** /var/tmp/temproot ready for use
     *** Creating and populating directory structure in /var/tmp/temproot

    Unknown modifier 't'

    Syntax error: Unterminated quoted string

      *** FATAL ERROR: Cannot 'cd' to /usr/src and install files to
          the temproot environment