RFR for CODETOOLS-7902292: defpath extension broken after util.Abort removed from hg in March 2018

[Tim Bell]

Hello

Abort() was moved/copied from util to error in hg 1.3 and was removed 
from util in hg 4.6

This is the same fix used on trees.py back in July [1].

http://cr.openjdk.java.net/~tbell/CODETOOLS-7902292/webrev/

Tested with hg versions 3.2.3, 4.7

Thanks in advance.  I will also need a sponsor to push the change for me.

Tim

[1] Ref lines 140 ... 146: 
http://hg.openjdk.java.net/code-tools/trees/comparison/592eba45b774/trees.py