Broken for Hg 4.4.2, Mac OS X 10.13.1
Created originally on Bitbucket by alexreg (Alexander Regueiro)
I get this when running any Hg command:
*** failed to import extension mercurial_keyring: <mercurial.cmdutil.command object at 0x10f386590> is not a Python function
Looks like a bug / compatibility issue.