Exception handling when the json OpenApi schema url is not found

[Agustin Jimenez]

First of all: YOU SOFTWARE IS AWESOME! THANKS!

So. When the json schema of an API is not founded, the software raises tracebacks.

Maybe implementing some exception handling will be a good Idea for finish the execution of the program more elegantly.

  $ http-prompt http://localhost:8000 --spec=<WRONG JSON SCHEMA>
Version: 1.0.0
Traceback (most recent call last):
  File "/usr/lib/python3.8/urllib/request.py", line 1350, in do_open
    h.request(req.get_method(), req.selector, req.data, headers,
  File "/usr/lib/python3.8/http/client.py", line 1255, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1301, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1250, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1010, in _send_output
    self.send(msg)
  File "/usr/lib/python3.8/http/client.py", line 950, in send
    self.connect()
  File "/usr/lib/python3.8/http/client.py", line 921, in connect
    self.sock = self._create_connection(
  File "/usr/lib/python3.8/socket.py", line 808, in create_connection
    raise err
  File "/usr/lib/python3.8/socket.py", line 796, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/__USERNAME__/.local/bin/http-prompt", line 8, in <module>
    sys.exit(cli())
  File "/usr/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/home/__USERNAME__/.local/lib/python3.8/site-packages/http_prompt/cli.py", line 110, in cli
    f = urlopen(spec)
  File "/usr/lib/python3.8/urllib/request.py", line 222, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.8/urllib/request.py", line 525, in open
    response = self._open(req, data)
  File "/usr/lib/python3.8/urllib/request.py", line 542, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
  File "/usr/lib/python3.8/urllib/request.py", line 502, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.8/urllib/request.py", line 1379, in http_open
    return self.do_open(http.client.HTTPConnection, req)
  File "/usr/lib/python3.8/urllib/request.py", line 1353, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [Errno 111] Connection refused>