fteproxy terminates abruptly on input of a bad format name

[kpdyer]

fteproxy handles invalid format names poorly. Instead, fteproxy should terminate with a helpful error message.

$ fteproxy --upstream-format badformatname
fteproxy Copyright (C) 2012-2014 Kevin P. Dyer <[email protected]>
    This program comes with ABSOLUTELY NO WARRANTY.
    This is free software, and you are welcome to redistribute it under certain conditions.

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/fteproxy/cli.py", line 163, in run
    outgoing_regex = fteproxy.defs.getRegex(self._args.upstream_format)
  File "/usr/local/lib/python2.7/site-packages/fteproxy/defs/__init__.py", line 50, in getRegex
    raise InvalidRegexName(format_name)
InvalidRegexName: badformatname
ERROR: FTEMain terminated unexpectedly: badformatname
  File "/usr/local/Cellar/python/2.7.8/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 783, in __bootstrap
    self.__bootstrap_inner()
  File "/usr/local/Cellar/python/2.7.8/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "/usr/local/lib/python2.7/site-packages/fteproxy/cli.py", line 210, in run
    fteproxy.fatal_error("FTEMain terminated unexpectedly: "+str(e))
  File "/usr/local/lib/python2.7/site-packages/fteproxy/__init__.py", line 53, in fatal_error
    traceback.print_stack()