AttributeError: 'module' object has no attribute 'RepositoryFormatCHK1'

I just came across this plugin. Unsurprisingly, it doesn't work with the latest Bazaar.

bzr: ERROR: exceptions.AttributeError: 'module' object has no attribute 'RepositoryFormatCHK1'

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 930, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 1121, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 673, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 697, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 136, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/home/asb/.bazaar/plugins/repodetails/__init__.py", line 51, in run
    import gather_stats
  File "/home/asb/.bazaar/plugins/repodetails/gather_stats.py", line 72, in <module>
    groupcompress_repo.RepositoryFormatCHK1,
AttributeError: 'module' object has no attribute 'RepositoryFormatCHK1'

ProblemType: Crash
DistroRelease: Ubuntu 14.04
Package: bzr 2.6.0+bzr6591-1ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-19.40-generic 3.13.6
Uname: Linux 3.13.0-19-generic x86_64
ApportVersion: 2.13.3-0ubuntu1
Architecture: amd64
BzrDebugFlags: set([])
BzrVersion: 2.7.0dev1
CommandLine: ['/usr/bin/bzr', 'repository-details', 'repodetails']
CrashDb: bzr
CurrentDesktop: Unity
Date: Fri Mar 28 12:47:55 2014
ExecutablePath: /usr/bin/bzr
FileSystemEncoding: UTF-8
InstallationDate: Installed on 2013-03-16 (376 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130316)
InterpreterPath: /usr/bin/python2.7
Locale: en_US.UTF-8
PackageArchitecture: all
Platform: Linux-3.13.0-19-generic-x86_64-with-Ubuntu-14.04-trusty
ProcCmdline: /usr/bin/python /usr/bin/bzr repository-details repodetails
PythonVersion: 2.7.6
SourcePackage: bzr
Title: bzr crashed with AttributeError in /home/username/.bazaar/plugins/repodetails/gather_stats.py: 'module' object has no attribute 'RepositoryFormatCHK1'
UpgradeStatus: Upgraded to trusty on 2013-12-07 (111 days ago)
UserEncoding: utf-8
UserGroups: adm autopilot cdrom dip libvirtd lpadmin plugdev sambashare sbuild sudo