raise errors on rspec deprecations

refs CNVS-16239

Change-Id: Ica174a75bbc621e77578457ab6ff7627fd4f8cfb
Reviewed-on: https://gerrit.instructure.com/42714
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>