fix cache test for macs. stupid bsd sed again

Author: dschep

test.bats

@@ -61,7 +61,7 @@ teardown() {
 @test "py3.6 uses cache with dockerizePip option" {
     [ -z "$CIRCLE_BRANCH" ] || skip "Volumes are weird in CircleCI https://circleci.com/docs/2.0/building-docker-images/#mounting-folders"
     ! uname -sm|grep Linux || groups|grep docker || id -u|egrep '^0$' || skip "can't dockerize on linux if not root & not in docker group"
-    sed -i'.bak' -re 's/(pythonRequirements:$)/\1\n    pipCmdExtraArgs: ["--cache-dir", ".requirements-cache"]/' serverless.yml
+    perl -p -i'.bak' -e 's/(pythonRequirements:$)/\1\n    pipCmdExtraArgs: ["--cache-dir", ".requirements-cache"]/' serverless.yml
     sls --dockerizePip=true package
     ls .requirements-cache/http
 }