AWS Lambda Python - Push part of MediaInfo function response to SNS

Question

firstly I am relatively new to code and attempting to teach myself what I need! I have managed to butcher bits of example code that I have found on various forums to get to where I am now. I am running an AWS Lambda function that triggers when a new file is uploaded to a bucket, and then sends the file off to MediaInfo (I built a self contained CLI executable that is uploaded to the Lambda function) the result of this is in XML format, and I have managed to pass this onto a DynamoDB database.

My question is - I want to export the XML produced by this function and push it to an SNS topic so that I can pick it up and use elsewhere (knack database). Here is my Lambda code in full (changed private info).

import logging
import subprocess

import boto3

SIGNED_URL_EXPIRATION = 300     # The number of seconds that the Signed 
URL is valid
DYNAMODB_TABLE_NAME = "demo_metadata"
DYNAMO = boto3.resource("dynamodb")
TABLE = DYNAMO.Table(DYNAMODB_TABLE_NAME)

logger = logging.getLogger('boto3')
logger.setLevel(logging.INFO)


def lambda_handler(event, context):
    """
:param event:
    :param context:
    """
    # Loop through records provided by S3 Event trigger
    for s3_record in event['Records']:
        logger.info("Working on new s3_record...")
        # Extract the Key and Bucket names for the asset uploaded to S3
        key = s3_record['s3']['object']['key']
        bucket = s3_record['s3']['bucket']['name']
        logger.info("Bucket: {} \t Key: {}".format(bucket, key))
        # Generate a signed URL for the uploaded asset
        signed_url = get_signed_url(SIGNED_URL_EXPIRATION, bucket, key)
        logger.info("Signed URL: {}".format(signed_url))
        # Launch MediaInfo
        # Pass the signed URL of the uploaded asset to MediaInfo as an 
input
        # MediaInfo will extract the technical metadata from the asset
        # The extracted metadata will be outputted in XML format and
        # stored in the variable xml_output
        xml_output = subprocess.check_output(["./mediainfo", "--full", "--output=XML", signed_url])
        logger.info("Output: {}".format(xml_output))
        save_record(key, xml_output)


def save_record(key, xml_output):
    """
    Save record to DynamoDB

    :param key:         S3 Key Name
    :param xml_output:  Technical Metadata in XML Format
    :return:            xml_output
    """
    logger.info("Saving record to DynamoDB...")
    TABLE.put_item(
       Item={
            'keyName': key,
            'technicalMetadata': xml_output
        }
    )
    logger.info("Saved record to DynamoDB")


def get_signed_url(expires_in, bucket, obj):
    """
    Generate a signed URL
    :param expires_in:  URL Expiration time in seconds
    :param bucket:
    :param obj:         S3 Key name
    :return:            Signed URL
    """
    s3_cli = boto3.client("s3")
    presigned_url = s3_cli.generate_presigned_url('get_object', Params= {'Bucket': bucket, 'Key': obj},
                                              ExpiresIn=expires_in)
    return presigned_url

The output I get from the Lambda function when using the aws GUI is here, and this is what I went to send to an SNS topic.

<Height>1080</Height>
<Height>1 080 pixels</Height>
<Stored_Height>1088</Stored_Height>
<Sampled_Width>1920</Sampled_Width>
<Sampled_Height>1080</Sampled_Height>
<Pixel_aspect_ratio>1.000</Pixel_aspect_ratio>
<Display_aspect_ratio>1.778</Display_aspect_ratio>
<Display_aspect_ratio>16:9</Display_aspect_ratio>
<Rotation>0.000</Rotation>
<Frame_rate_mode>CFR</Frame_rate_mode>
<Frame_rate_mode>Constant</Frame_rate_mode>
<Frame_rate>29.970</Frame_rate>
<Frame_rate>29.970 (30000/1001) fps</Frame_rate>
<FrameRate_Num>30000</FrameRate_Num>
<FrameRate_Den>1001</FrameRate_Den>
<Frame_count>630</Frame_count>
<Resolution>8</Resolution>
<Resolution>8 bits</Resolution>
<Colorimetry>4:2:0</Colorimetry>
<Color_space>YUV</Color_space>
<Chroma_subsampling>4:2:0</Chroma_subsampling>
<Chroma_subsampling>4:2:0</Chroma_subsampling>
<Bit_depth>8</Bit_depth>
<Bit_depth>8 bits</Bit_depth>
<Scan_type>Progressive</Scan_type>
<Scan_type>Progressive</Scan_type>
<Interlacement>PPF</Interlacement>
<Interlacement>Progressive</Interlacement>
<Bits__Pixel_Frame_>0.129</Bits__Pixel_Frame_>
<Stream_size>21374449</Stream_size>
<Stream_size>20.4 MiB (99%)</Stream_size>
<Stream_size>20 MiB</Stream_size>
<Stream_size>20 MiB</Stream_size>
<Stream_size>20.4 MiB</Stream_size>
<Stream_size>20.38 MiB</Stream_size>
<Stream_size>20.4 MiB (99%)</Stream_size>
<Proportion_of_this_stream>0.98750</Proportion_of_this_stream>
<Encoded_date>UTC 2017-11-24 19:29:16</Encoded_date>
<Tagged_date>UTC 2017-11-24 19:29:16</Tagged_date>
<Buffer_size>16000000</Buffer_size>
<Color_range>Limited</Color_range>
<colour_description_present>Yes</colour_description_present>
<Color_primaries>BT.709</Color_primaries>
<Transfer_characteristics>BT.709</Transfer_characteristics>
<Matrix_coefficients>BT.709</Matrix_coefficients>
</track>

<track type="Audio">
<Count>272</Count>
<Count_of_stream_of_this_kind>1</Count_of_stream_of_this_kind>
<Kind_of_stream>Audio</Kind_of_stream>
<Kind_of_stream>Audio</Kind_of_stream>
<Stream_identifier>0</Stream_identifier>
<StreamOrder>1</StreamOrder>
<ID>2</ID>
<ID>2</ID>
<Format>AAC</Format>
<Format_Info>Advanced Audio Codec</Format_Info>
<Commercial_name>AAC</Commercial_name>
<Format_profile>LC</Format_profile>
<Codec_ID>40</Codec_ID>
<Codec>AAC LC</Codec>
<Codec>AAC LC</Codec>
<Codec_Family>AAC</Codec_Family>


</File>
</Mediainfo>


[INFO]  2018-04-22T18:50:01.803Z    efde8294-465d-11e8-9ad2-0db0d6b36746    Saving record to DynamoDB...
[INFO]  2018-04-22T18:50:02.21Z efde8294-465d-11e8-9ad2-0db0d6b36746     
Saved record to DynamoDB
END RequestId: efde8294-465d-11e8-9ad2-0db0d6b36746
REPORT RequestId: efde8294-465d-11e8-9ad2-0db0d6b36746  Duration: 9769.02 ms    Billed Duration: 9800 ms    Memory Size: 128 MB Max Memory Used: 61 MB  

Many thanks in advance to anyone with advice!