tests: show bad path auditing in in-memory rebase
Thanks to Yuya for providing this test case in
https://bz.mercurial-scm.org/show_bug.cgi?id=5818.
Differential Revision: https://phab.mercurial-scm.org/D5368
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\nOK.