isenabled() breaks keyring for older mercurial versions
Created originally on Bitbucket by eraserix (Christoph Mathys)
After updating to 0.6.3 on Ubuntu 14.04 (current LTS) I get the following error when firing up hg:
$ hg out *** failed to import extension mercurial_keyring from mercurial_keyring.py: 'module' object has no attribute 'isenabled'
14.04 ships with mercurial 2.8.2. The function isenabled() however was not part of mercurial until 2.9.1.