py3: make check-py3-compat.py use correct module name at loading pure modules Before this patch, check-py3-compat.py implies unintentional ".pure" sub-package name at loading pure modules, because module name is composed by just replacing "/" in the path to actual ".py" file by ".". This makes pure modules belong to "mercurial.pure" package, and prevents them from importing a module belonging to "mercurial" package relatively by "from . import foo" or so. This is reason why pure modules fail to import another module relatively only at examination by check-py3-compat.py.