BranchBuilder tests are not properly isolated

[Andrew Bennetts]

John Arbash Meinel wrote:
[...]
> 1) The bzrlib.branchbuilder doc tests do not isolate their environment.
> Specifically, I have a default policy to sign all commits. And when
> those tests run, it asks for my gpg key. I'm not really sure what to do
> here, but it is annoying. (made more obvious because Hardy's gpg-agent
> defaults to prompting for your approval before using a cached passphrase.)

I already reported this one a while back:
<https://bugs.launchpad.net/bzr/+bug/321320>

As I say on the bug:

“A good fix would probably be to change the way we construct DocTestSuite.
We could pass setUp and tearDown params to its constructor to do the same
sort of setUp and tearDown as we do in normal TestCases. In particular do
the isolation of the test environment from the user's normal day-to-day
environment.”

-Andrew.