crash on HTTP 401 error

[ktdreyer]

chacractl binary create <endpoint> <binaryfile> prints a stack trace if I have the wrong key in my ~/.chacractl:

Traceback (most recent call last):
  File "venv/bin/chacractl", line 6, in <module>
    main.ChacraCtl()
  File "venv/local/lib/python2.7/site-packages/chacractl/main.py", line 37, in __init__
    self.main(argv)
  File "venv/local/lib/python2.7/site-packages/chacractl/decorators.py", line 68, in newfunc
    return f(*a, **kw)
  File "venv/local/lib/python2.7/site-packages/chacractl/main.py", line 80, in main
    parser.dispatch()
  File "venv/local/lib/python2.7/site-packages/tambo/dispatcher.py", line 21, in dispatch
    return instance.main()
  File "venv/local/lib/python2.7/site-packages/chacractl/api/binaries.py", line 123, in main
    self.post(url, filename)
  File "venv/local/lib/python2.7/site-packages/chacractl/api/binaries.py", line 80, in post
    response.raise_for_status()
  File "venv/local/lib/python2.7/site-packages/requests/models.py", line 837, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 401 Client Error: Unauthorized for url: https://chacra.example.com/binaries/myproject/myref/ubuntu/trusty/source/

It's probably better to catch the HTTPError and print an explanation to the user about what could have gone wrong.