Catch illegal boolean values in hgrc nicely.
With hg 0.9.3 the section and parameter name wasn't printed,
with hg 0.9.4 there was a traceback for ValueError.
To run the tests, do:cd tests/python run-tests.pySee http://www.selenic.com/mercurial/wiki/index.cgi/WritingTests formore information on writing tests.