[RFH] bzr 2.1.0rc + scmproj selftest: "attempt to escape test isolation". What should I do?

[Alexander Belchenko]

Dear bzr devs,

Can you have some docs or exampples of how I should port my tests in 
scmproj plugin to be compatible with both bzr 2.1.0rc1 and bzr 2.0? I 
have 5 failures and all of them are about "Attempt to escape test 
isolation".

Thanks
Alexander