Comment # 6 on bug 1155271 from Michael Matz

I think the package fails because of the unexpected pass of backref-alt (the
XPASS), not because of triple-backref.  backref-alt starts working with glibc
2.28 and was changed to not be an xfail anymore in grep, but obviously grep 3.1
still contains the expectation that this test should fail, which it doesn't
anymore (because fixes in glibc).

(grep commit c505b0bce)