import-checker: increase portability for python 2.6.x Before this patch, fromlocalfunc() assumes that "module" attribute of ast.ImportFrom is None for "from . import a", and Python 2.7.x satisfies this assumption. On the other hand, with Python 2.6.x, "module" attribute of ast.ImportFrom is an empty string for "from . import a", and this causes failure of test-check-module-imports.t.