Fix handling of people

Bugs that are created on Trac make the program crash.
Some bugs that are created on Trac make the program crash.

'''Crash is fixed! '''

Cause
    name: "" was internally translated to "*" which was not handled specially in people_intl2repo.

* Write tests that create such problematic bugs, and tries to synchronize them.

* Create new bug report: Unknown names are replaced by "*" on Trac.

{{{
Traceback (most recent call last):
  File "../../bsync.py", line 31, in <module>
    bsync.main()
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/main.py", line 96, in main
    self.do_sync(cmdinfo)
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/main.py", line 258, in do_sync
    syncer.synchronize_repos()
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/main.py", line 835, in synchronize_repos
    self.write_bugs(write_tasks)
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/main.py", line 801, in write_bugs
    new_ids = ctrl.create_bugs(bugs_create[repo_name])
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/repo_io.py", line 697, in create_bugs
    self.bug_internal2launchpad(bug, lp_task, lp_bug)
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/repo_io.py", line 722, in bug_internal2launchpad
    lp_assignee_name = self.people_intl2repo(my_bug.assigned_to)
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/repo_io.py", line 94, in people_intl2repo
    return self.people_translator.intl2repo(self.repo_name, name)
  File "/home/eike/codedir/z-eclipse-workspace/bug_syncer/trunk/src/bug_syncer/common.py", line 321, in intl2repo
    raise UnknownWordError(word)
bug_syncer.common.UnknownWordError: '*'
}}}