ancestor: use absolute_import A few months ago, import-checker.py was taught to enforce a more well-defined import style for files with absolute_import. However, we stopped short of actually converting source files to use absolute_import because of problems with certain files. Investigation revealed the following problems with switching to absolute_import universally: 1) import cycles result in import failure on Python 2.6 2) undetermined way to import C/pure modules While these problems need to be solved, they can be put off. This patch starts a series of converting files to absolute_import that won't exhibit any of the aforementioned problems.