I ran the test case in an up-to-date xenial VM, and verified that it failed. I then enabled xenial-proposed (universe) and installed cargo 0.37.0-3ubuntu1~16.04.2, ran the test case again, and verified that it passed.
I ran the test case in an up-to-date xenial VM, and verified that it failed. 3ubuntu1~ 16.04.2, ran the test case again, and verified that it passed.
I then enabled xenial-proposed (universe) and installed cargo 0.37.0-