Use the builtin Terraform behaviour for updating Lambdas

terraform/lambda/lambda_function.tf

@@ -5,12 +5,13 @@ data "archive_file" "lambda_zip_file" {
 }
 
 resource "aws_lambda_function" "lambda_function" {
-  description   = "${var.description}"
-  filename      = "${data.archive_file.lambda_zip_file.output_path}"
-  function_name = "${var.name}"
-  role          = "${aws_iam_role.iam_role.arn}"
-  handler       = "${var.name}.main"
-  runtime       = "python3.6"
+  description      = "${var.description}"
+  filename         = "${data.archive_file.lambda_zip_file.output_path}"
+  function_name    = "${var.name}"
+  role             = "${aws_iam_role.iam_role.arn}"
+  handler          = "${var.name}.main"
+  runtime          = "python3.6"
+  source_code_hash = "${data.archive_file.lambda_zip_file.output_base64sha256}"
 
   environment {
     variables = "${var.environment_variables}"

terraform/plan.sh

@@ -20,10 +20,6 @@ rm -rf releases
 echo "Getting variables from S3"
 aws s3 cp s3://platform-infra/terraform.tfvars .
 
-# Check if any of our Lambda packages have changed and need to be tainted.
-# Annoyingly there doesn't seem to be a way for Terraform to do this for us.
-python taint_lambdas.py
-
 # Download releases from S3
 mkdir releases
 aws s3 cp s3://platform-infra/releases releases --recursive