Work around different versions of patch(1) in unit tests

Review Request #10164 — Created Sept. 22, 2018 and submitted — Latest diff uploaded


Review Board


We had a unit test that depended on the specific version of patch(1)
installed. Newer versions of patch will accept a diff that contains no
hunks, whereas older versions will fail with a message saying that the
input contained only garbage.

We now have unit tests that check the correct behaviour happens in both
cases by replacing our call to patch(1).

Ran unit tests.