Comment 1 for bug 1607974

I am also experiencing this:

17:00:11 Calculating the revisions to include ...
17:00:11 Starting export of 261 revisions ...
bzr: ERROR: exceptions.TypeError: cannot concatenate 'str' and 'int' objects

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/ben/.bazaar/plugins/fastimport/cmds.py", line 720, in run
    return exporter.run()
  File "/home/ben/.bazaar/plugins/fastimport/exporter.py", line 240, in run
    self.emit_commit(revid, self.ref)
  File "/home/ben/.bazaar/plugins/fastimport/exporter.py", line 358, in emit_commit
    self.print_cmd(self._get_commit_command(ref, mark, revobj, file_cmds))
  File "/home/ben/.bazaar/plugins/fastimport/exporter.py", line 441, in _get_commit_command
    more_authors=more_author_info, properties=properties)
  File "/home/ben/.local/lib/python2.7/site-packages/fastimport/commands.py", line 168, in __init__
    self.id = b':' + mark
TypeError: cannot concatenate 'str' and 'int' objects

bzr 2.7.0 on python 2.7.11 (Linux-4.4.0-21-generic-x86_64-with-
    Ubuntu-16.04-xenial)
arguments: ['/usr/bin/bzr', 'fast-export', '--export-marks=../marks.bzr', '.']
plugins: bash_completion[2.7.0], changelog_merge[2.7.0],
    fastimport[0.14.0dev], grep[2.7.0], launchpad[2.7.0],
    netrc_credential_store[2.7.0], news_merge[2.7.0], po_merge[2.7.0],
    weave_fmt[2.7.0]
encoding: 'utf-8', fsenc: 'UTF-8', lang: 'en_AU.UTF-8'

*** Bazaar has encountered an internal error. This probably indicates a
    bug in Bazaar. You can help us fix it by filing a bug report at
        https://bugs.launchpad.net/bzr/+filebug
    including this traceback and a description of the problem.