Python - FFMPEG - Test to see if video file contains DTS audio

I'm currently running a script on cron job to convert any video files to .mp4 from .mkv. I use FFMPEG and python 2.7 to accomplish this on FreeBSD and do a native copy for both audio and video which means I leave whatever encoding they use but convert the container mkv to mp4 for DLNA because of compatibility issues for some devices. Some files contain DTS and I want to convert those audio file to AAC/AC3. I only want to convert and trans code audio to AAC/AC3 only if the file has only single audio of DTS. Some files do have DTS and AAC so I would only want to remove the DTS and not trans code in those cases. Is there way I can test a video file and see it if contains a DTS? Any software I can use like FFMPEG or handbrake? How would you go about do this? I'm trying to not lose any quality.

Psuede Code:

If file contains DTS:
    If file only has single audio track:
        convert_to_mp4_AAC_5.1()
    else:
        remove_DTS(file)
        convert_native()
else:
    convert_native()