Matching the HTML for regexps does not work reliably when we have multiple
unstable packages of which only some are valid candidates but others aren't. It
also imposes a too strict test on the particular formatting when we are only
interested in the actual data and structure.
So move towards checking the machine parseable YAML instead and read that into
a proper Python dict.
This exposed a bug uncovered by test_rdepends_unbuilt() which we previously
missed because we couldn't check triggered tests per package.
Don't change britney.conf from the source tree and restore it back after the
tests; this is prone to leave a broken config behind if a test gets
interrupted. Instead, copy the file to our temp dir, and let tests hack on it
there.
(Introduced in lp:~canonical-ci-engineering/britney/boottesting-support)
Extend read_sources to store a new AUTOPKGTEST boolean flag, which is true if
the Testsuite: field exists and starts with "autopkgtest" (this covers autodep8
cases like autopkgtest-pkg-perl).
Extend TestData.add() to take a new testsuite argument which specifies the
source's Testsuite: field.
