Code review comment for lp:~james-w/launchpad/create-source-recipe-build

This adds a requestBuild method to SourcePackageRecipe, allowing you
to request that the recipe be built in to a specific archive.

There is a TODO which can be removed and the assertion uncommented
when the prerequisite branch is fixed to implement the interface
correctly.

There are a few other changes necessary to do this elegantly:

  The objects returned from check_upload_to_archive now derive from
  Exception so that we can raise them directly. This shouldn't affect
  existing code.

  check_upload_to_archive now checks for disabled archives, and this
  is moved out of processupload.py

Thanks,

James