itersubrepos: move to scmutil to break a direct import cycle

import-checker: handle standard modules with arch in the filename Installations with module names like /usr/lib/python2.7/lib-dynload/bz2.x86_64-linux-gnu.so occurs in the wild. Let's just ignore everything after first '.' when guessing the Python module name.

tests: use ls instead of find, all files are in the same directory In this case find has no advantage compared to ls. Descending into directories is unnecessary, because there are none.