[MERGE] Make the test suite pass when -Eallow_debug is used.

[Vincent Ladeuil]

>>>>> "Andrew" == Andrew Bennetts <andrew at canonical.com> writes:

    Andrew> Vincent Ladeuil wrote:
    Andrew> [...]
    >> Banging again.
    >> 
    >> Damn it, I didn't see that one lands and can't remember how often
    >> I pestered about the inability to use -Dhttp while running some
    >> tests :-(

    Andrew> D'oh!  Oh well, now you know.  I hope it helps!  I've certainly found it
    Andrew> helpful to have -Dhpss enabled in tests from time to time.

    Andrew> It's confusing to have unrelated failures appear when
    Andrew> you turn debugging options on :)
    >> 
    >> But... where are the tests ? :D
    >> 
    >> BB:tweak

    Andrew> What test(s) do you have in mind?  A test that
    Andrew> debug_flags are restored by TestCase, whether or not
    Andrew> they are cleared?

A test reproducing the bug you just fixed.

And one test that ensures that -Eallow_debug has an
effect. Either by a selftest blackbox test or a test around
TestCase._clear_debug_flags or a single for both.

More prophylactic than strictly required but it will help the day
we add another selftest_debug_flag (I had to read '-E' twice because I
thought you made a typo for -Dallow_debug :).

  Vincent