Unfortunately there are a few places in the buildhistory web interface code that hardcode the directory name that it must be installed into as "warningmanager" (due to python module references). Django provides little documentation on how to make your application easily distributable and installable so we will just have to fix it directly.
Fixed in buildhistory-web master: http://git.yoctoproject.org/cgit/cgit.cgi/buildhistory-web/commit/?id=fd4f3e362f159f7c75db19f2a227712fe26afa94
Verified in buildhistory-web: 473c6c505ea7ed0475dd686e8662753b2f831abf