AttributeError during process finish with keyring >= 16.0.1
Originally reported to the hg bug tracker:
https://bz.mercurial-scm.org/show_bug.cgi?id=6043
I wonder if the change in hg 8e89c2bec1f7 unmasked an existing problem. OTOH, it doesn't appear to be a problem with TortoiseHg 4.6.1, which shipped 1.1.8.