An error occurred (AllAccessDisabled) when calling the ListObjects operation

Question

I might be missing something and could use a 2nd pair of eyes on these policies.

My bucket policy :

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowS3Access",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::redacted:role/myrole"
            },
            "Action": "s3:*",
            "Resource": [
                "arn:aws:s3:::<my-bucket>",
                "arn:aws:s3:::<my-bucket>/*"
            ]
        }
    ]
}

I checked the object permissions and for the only object in there I allow read and write access by everyone just to get this function to work (but it still does not).

Here is the lambda role I am using to access the bucket:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "s3:PutObject",
                "s3:GetObject",
                "dynamodb:GetItem",
                "s3:ListBucket",
                "dynamodb:Query",
                "dynamodb:UpdateItem",
                "s3:DeleteObject",
                "s3:GetBucketLocation",
                "s3:PutObjectAcl"
            ],
            "Resource": [
                "arn:aws:s3:::<my-bucket>",
                "arn:aws:s3:::<my-bucket>/*",
                "arn:aws:dynamodb:us-east-1:dynamo:table/myTable"
            ]
        },
        {
            "Sid": "VisualEditor1",
            "Effect": "Allow",
            "Action": [
                "polly:SynthesizeSpeech",
                "polly:StartSpeechSynthesisTask",
                "s3:ListAllMyBuckets",
                "polly:GetSpeechSynthesisTask"
            ],
            "Resource": "*"
        }
    ]
}

Could it be that the function I am writing in lambda is wrong? Here is the part it breaks at:

s3 = boto3.resource('s3')
bucket = s3.Bucket('BUCKET_NAME')
key = postId + "_" + title + ".mp3"
objs = list(bucket.objects.filter(Prefix=key))
if len(objs) > 0 and objs[0].key == key:
   print("Exists!")
   boto3.client('s3').delete_object(Bucket='BUCKET_NAME', Key=key)
else:
  print("Doesn't exist")

I tried adding in ListObject as a policy action but I think it is just related to List bucket. I pulled the list bucket objects function from another answer because I am new at Python, but still seems like it should work at this point.

EDIT: Here is the exact error I receive in cloudwatch

An error occurred (AllAccessDisabled) when calling the ListObjects 
  operation: All access to this object has been disabled: ClientError
  Traceback (most recent call last):
  File "/var/task/lambda_function.py", line 33, in lambda_handler

EDIT 2: BUCKET_NAME is an environmental variable.

Answer 1

I was assigning environmental variables incorrectly. The correct syntax is

    s3 = boto3.resource('s3', 'us-east-1')
    bucket_name = os.environ['BUCKET_NAME'] <<<< this variable
    bucket = s3.Bucket(bucket_name) <<<<< into here

to assign environmental variables to your lambda code.