code: def _machine_check_connectivity():
      
      with open(devnull, 'w') as devnull_f:
          try:
              status = subprocess.check_output(
                  ['docker-machine', 'status', 'dev'],
                  stderr=devnull_f).strip()
              if status == 'Stopped':
                  raise DatacatsError('Please start your docker-machine '
                                      'VM with "docker-machine start dev"')
  
              # XXX HACK: This exists because of
              #           http://github.com/datacats/datacats/issues/63,
              # as a temporary fix.
              if 'tls' in _docker_kwargs:
                  # It will print out messages to the user otherwise.
                  _docker_kwargs['tls'].assert_hostname = False
          except subprocess.CalledProcessError:
              raise DatacatsError('Please create a docker-machine with '
                                  '"docker-machine start dev"')
docs: This method calls to docker-machine on the command line and
      makes sure that it is up and ready.
  
      Potential improvements to be made:
          - Support multiple machine names (run a `docker-machine ls` and then
          see which machines are active. Use a priority list)