logm robustness

[Tommy Guy]

logm is using eigenvalues, which was listed as lacking robustness.
While it does appear that a Schur or Schur-Parlett algorithm would be
more robust for logarithm, I'm having trouble finding an instance
where the eigenvalue approach is not robust.  Does anyone have an
example where this might occur?

I am willing to include it as a test case in the .m file if anyone can
come up with something.

Richard T. Guy