Make importlib compatible with __import__ by "fixing" code.co_filename paths. __import__ does a little trick when importing from bytecode by back-patching the co_filename paths to point to the file location where the code object was loaded from, *not* where the code object was originally created. This allows co_filename to point to a valid path. Problem is that co_filename is immutable from Python, so a private function -- imp._fix_co_filename() -- had to be introduced in order to get things working properly. Originally the plan was to add a file argument to marshal.loads(), but that failed as the algorithm used by __import__ is not fully recursive as one might expect, so to be fully backwards-compatible the code used by __import__ needed to be exposed. This closes issue #6811 by taking a different approach than outlined in the issue.