load extensions only after the ui object has been completely initialized This fixes a traceback printed when hg tries to print another traceback after an extension fails to be loaded. Add a test for that.

#!/bin/sh

mkdir a
cd a
hg init
echo foo > b
hg add b
hg ci -m "b" -d "1000000 0"

chmod -w .hg

cd ..

hg clone a b

chmod +w a/.hg # let test clean up

cd b
hg verify