Warn if Doxycannon (containers) are already running

[routeback]

If you try to start DoxyCannon after you already have containers running, it will provide a very long error message and stop accepting terminal input (Ctrl + C will not break, must kill DoxyCannon process manually in another terminal).

Is it possible to add a check for running containers that match the *.ovpn configuration files and notify the user that 'The cannon is already armed' prior to performing any work?

root@:$ ./doxycannon.py --build
[*] Image audibleblink/doxycannon built.
root@:$ ./doxycannon.py --up
[+] Writing HAProxy configuration
[+] Writing Proxychains4 configuration
Starting: us-tx-108.protonvpn.com.udp1194
Starting: us-il-105.protonvpn.com.udp1194
Starting: us-nj-04.protonvpn.com.udp1194
Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "./doxycannon.py", line 166, in multistart
    detach=True)
  File "/usr/local/lib/python2.7/dist-packages/docker/models/containers.py", line 766, in run
    detach=detach, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/docker/models/containers.py", line 824, in create
    resp = self.client.api.create_container(**create_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/container.py", line 411, in create_container
    return self.create_container_from_config(config, name)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/container.py", line 422, in create_container_from_config
    return self._result(res, True)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/client.py", line 235, in _result
    self._raise_for_status(response)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/client.py", line 231, in _raise_for_status
    raise create_api_error_from_http_exception(e)
  File "/usr/local/lib/python2.7/dist-packages/docker/errors.py", line 31, in create_api_error_from_http_exception
    raise cls(e, response=response, explanation=explanation)
APIError: 409 Client Error: Conflict ("Conflict. The container name "/us-il-105.protonvpn.com.udp1194" is already in use by container "9103148a541a0cc19ea824b1290e179f85a1f8067bd091f762aa0f4fc79b29ad". You have to remove (or rename) that container to be able to reuse that name.")
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "./doxycannon.py", line 166, in multistart
    detach=True)
  File "/usr/local/lib/python2.7/dist-packages/docker/models/containers.py", line 766, in run
    detach=detach, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/docker/models/containers.py", line 824, in create
    resp = self.client.api.create_container(**create_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/container.py", line 411, in create_container
    return self.create_container_from_config(config, name)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/container.py", line 422, in create_container_from_config
    return self._result(res, True)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/client.py", line 235, in _result
    self._raise_for_status(response)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/client.py", line 231, in _raise_for_status
    raise create_api_error_from_http_exception(e)
  File "/usr/local/lib/python2.7/dist-packages/docker/errors.py", line 31, in create_api_error_from_http_exception
    raise cls(e, response=response, explanation=explanation)
APIError: 409 Client Error: Conflict ("Conflict. The container name "/us-tx-108.protonvpn.com.udp1194" is already in use by container "9c850136d9effbe6cd5b310c4302850bc4160788a858296c57e6276b57c1bf0a". You have to remove (or rename) that container to be able to reuse that name.")

Exception in thread Thread-3:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "./doxycannon.py", line 166, in multistart
    detach=True)
  File "/usr/local/lib/python2.7/dist-packages/docker/models/containers.py", line 766, in run
    detach=detach, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/docker/models/containers.py", line 824, in create
    resp = self.client.api.create_container(**create_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/container.py", line 411, in create_container
    return self.create_container_from_config(config, name)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/container.py", line 422, in create_container_from_config
    return self._result(res, True)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/client.py", line 235, in _result
    self._raise_for_status(response)
  File "/usr/local/lib/python2.7/dist-packages/docker/api/client.py", line 231, in _raise_for_status
    raise create_api_error_from_http_exception(e)
  File "/usr/local/lib/python2.7/dist-packages/docker/errors.py", line 31, in create_api_error_from_http_exception
    raise cls(e, response=response, explanation=explanation)
APIError: 409 Client Error: Conflict ("Conflict. The container name "/us-nj-04.protonvpn.com.udp1194" is already in use by container "29dc5360e957294ce41683a57bda9b624ee926230ef7f49e732a41bab22c389b". You have to remove (or rename) that container to be able to reuse that name.")

[audibleblink]

good call

[audibleblink]

I like this idea and I have an idea on how I'd like to handle it, but it warrants a new Major release, by SemVer standards. For now, I'll just proved a less verbose log of the issue with #24