Refactor formatting error path for yaml errors into separate method
Fix handling new style assistants (without top level name-attrs mapping) by cache
Always raise an error from assistant_from_yaml when assistant is malformed
Properly handle new style assistants everywhere
If there is a yaml error, don't try to go on running the assistant in path_runner
Further improve the yaml error messages, check dependencies sections recursively. #152
Code cleanups, removing unneeded imports
Try to follow pep8 more closely as required in bug #135
More pep8 fixes as required in #135
Implement checking run sections
Pull out the checking functionality out of LoadedYaml in a separate library-like file