Comment 3 for bug 408824

I agree it is confusing, but it's not due to my plugin: when I run it in a copy of your bug 398668 branch with no plugins, I still get

3.752 Traceback (most recent call last):
  File "/home/mbp/bzr/398668-2a-default/bzrlib/commands.py", line 1131, in run_bzr_catch_user_errors
    return run_bzr(argv)
  File "/home/mbp/bzr/398668-2a-default/bzrlib/commands.py", line 1030, in run_bzr
    ret = run(*run_argv)
  File "/home/mbp/bzr/398668-2a-default/bzrlib/commands.py", line 647, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/mbp/bzr/398668-2a-default/bzrlib/builtins.py", line 3140, in run
    upgrade(url, format)
  File "/home/mbp/bzr/398668-2a-default/bzrlib/upgrade.py", line 85, in upgrade
    Convert(url, format)
  File "/home/mbp/bzr/398668-2a-default/bzrlib/upgrade.py", line 40, in __init__
    self.convert()
  File "/home/mbp/bzr/398668-2a-default/bzrlib/upgrade.py", line 74, in convert
    self.bzrdir.check_conversion_target(format)
  File "/home/mbp/bzr/398668-2a-default/bzrlib/bzrdir.py", line 134, in check_conversion_target
    source_repo_format.check_conversion_target(target_repo_format)
  File "/home/mbp/bzr/398668-2a-default/bzrlib/repofmt/groupcompress_repo.py", line 1101, in check_conversion_target
    'Does not support rich root data.', target_format)
BadConversionTarget: Cannot convert to format <RepositoryFormatKnit1>. Does not support rich root data.

3.753 errors:
'bzr: ERROR: Cannot convert to format <RepositoryFormatKnit1>. Does not support rich root data.\n'
3.759 opening working tree '/tmp/testbzr-D9P2yF.tmp'

^^^^[log from bzrlib.tests.blackbox.test_upgrade.TestWithUpgradableBranches.test_upgrade_explicit_knit]
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/mbp/bzr/398668-2a-default/bzrlib/tests/blackbox/test_upgrade.py", line 129, in test_upgrade_explicit_knit
    ['upgrade', '--format=knit', url])
AssertionError: Unexpected return code
not equal:
a = 0
b = 3