Got broken after upgrading Ubuntu to 16.04
Created originally on Bitbucket by matteosistisette (matteo sisti sette)
I had mercurial and the mercurial_keyring plugin installed and working just fine on Ubuntu 15.10.
After upgrading to 16.04, the mercurial_keyring extension doesn't work anymore, and every time I run any mercurial command I get this error:
*** failed to import extension mercurial_keyring: No module named builtins
(I'm not 100% sure it's always exactly the same, I think so; certainly it's always "*** failed [something] mercurial_keyring [something]")