- Implement validation abstraction that will use either lxml (Python lib) or xmllint (command line app) dependending on what is available - with test cases.
 - Add a ``--xsd`` flag to the lint command that lints against the experimental XSD from https://github.com/JeanFred/Galaxy-XSD.
 - Implement ``repository_dependencies.xsd`` to describe Tool Shed ``repository_dependencies.xml`` files (fairly complete).
 - Implement ``tool_dependencies.xsd`` to describe Tool Shed ``tool_dependencies.xml`` files.
   - Validates attributes and elements down to the ``action`` elements and then largely gives up (sticking ``any`` and ``anyAttribute`` tags on that element).
   - Registers everything in tools-devteam as valid, and detects one invalid XML file in tools-iuc.
 - Implement new ``shed_lint`` command that:
   - Validates tool_dependencies.xml against schema
   - Validates repository_dependencies.xml against schema
   - Bare minimum to lint .shed.yml files.
   - Optionally also lints tools in repsitories with the ``--tools`` argument.
   - Can recursively lint many repositories at ont time ``-r``.
 - Refactoring of existing stuff to support this and make room for XSD validation of tool XML files and generalizing applying actions over many repositories and many tools.