commands: call ui.username carefully in debuginstall
After
c63c336ee2f7, 'hg debuginstall' would abort halfway through if
no username was set. We now catch and display the exception instead.
#!/bin/sh
echo '% hg debuginstall'
hg debuginstall
echo '% hg debuginstall with no username'
HGUSER= hg debuginstall
# Happy End
true