Previously we weren't linting, there's a number of warning but there was
only one actual error reported when linting was enabled. It was
erroring on a valid usage of a single quoted variable-like string.
To allow linting to succeed (and the warning to show themselves) I've
disable the check that is giving a false positive.
These targets automate the fixtures directory using a configuration stored in
fixtures.yml. Because we can now handle the fixtures directory with a rake task,
the clone commands have been removed from the Travis config.
This commit adds test coverage for apt::ppa.
This test coverage is suficient to verify the
code changes that resolve the issue with
aptitude update not being called when ppas were
added (#10451).
