exception when listing customfield of type multiuser

[ckhan]

If a custom field is of type multi user picker, then attempting to list that field will result in an exception:

$ jira-cli view --format '%key;%customfield_11201' BUG-2015
Traceback (most recent call last):
  File "/usr/bin/jira-cli", line 11, in <module>
    load_entry_point('jira-cli==2.2', 'console_scripts', 'jira-cli')()
  File "/usr/lib/python/jiracli/interface.py", line 272, in cli
    return post_args.cmd(jira, post_args).execute()
  File "/usr/lib/python/jiracli/processor.py", line 30, in execute
    return self.eval()
  File "/usr/lib/python/jiracli/processor.py", line 75, in eval
    comments_only=self.args.comments_only
  File "/usr/lib/python/jiracli/bridge/__init__.py", line 68, in format_issue
    ret_str = ret_str.replace(k, issue.setdefault(v.lower(),"")).encode('utf-8')
TypeError: expected a string or other character buffer object

The behavior I'd like to see is detect that the field is a list of users, and concatenate the displayName property of each into a comma-separated list:

BUG-2015;Jane Doe,John Smith

Ugly hack I used to workaround this, in case useful to others before proper support added:

replaceValue = issue.setdefault(v.lower(),"")
if type(replaceValue) == list:
    replaceValue = ",".join(d.displayName for d in replaceValue)
ret_str = ret_str.replace(k, replaceValue).encode('utf-8')