Unreachable host - better error message?

[uSpike]

testinfra 1.14.1
ansible 2.6.3 (really any version)

It seems that if a host is unreachable with the ansible backend, you might get a traceback like:

 =================================== FAILURES===================================
     test_apt_transport_https_is_installed[ansible://molecule-test-bionic] 
    
    host = <testinfra.host.Host object at 0x7efccc5f8390>
    
        def test_apt_transport_https_is_installed(host):
    >       assert host.package("apt-transport-https").is_installed
    
    tests/roles/common/test_default.py:3:
    _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
    ../../venv/local/lib/python2.7/site-packages/testinfra/host.py:91: in __getattr__
        obj = module_class.get_module(self)
    ../../venv/local/lib/python2.7/site-packages/testinfra/modules/base.py:33: in get_module
        klass = cls.get_module_class(_host)
    ../../venv/local/lib/python2.7/site-packages/testinfra/modules/package.py:68: in get_module_class
        if host.system_info.type == "freebsd":
    ../../venv/local/lib/python2.7/site-packages/testinfra/modules/systeminfo.py:124: in type
        return self.sysinfo["type"]
    ../../venv/local/lib/python2.7/site-packages/testinfra/utils/__init__.py:42: in __get__
        value = obj.__dict__[self.func.__name__] = self.func(obj)
    ../../venv/local/lib/python2.7/site-packages/testinfra/modules/systeminfo.py:33: in sysinfo
        sysinfo["type"] = self.check_output("uname -s").lower()
    ../../venv/local/lib/python2.7/site-packages/testinfra/host.py:55: in run
        return self.backend.run(command, *args, **kwargs)
    _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
    

    self = <testinfra.backend.ansible.AnsibleBackend object at 0x7efccc5f8110>
    command = 'uname -s', args = (), kwargs = {}, out = {}
    
        def run(self, command, *args, **kwargs):
            command = self.get_command(command, *args)
            out = self.run_ansible("shell", module_args=command)
            return self.result(
    >           out['rc'],
                command,
                stdout_bytes=None,
                stderr_bytes=None,
                stdout=out["stdout"], stderr=out["stderr"],
            )
    E       KeyError: u'rc'
    
    ../../venv/local/lib/python2.7/site-packages/testinfra/backend/ansible.py:44: KeyError
    ----------------------------- Captured stderr call -----------------------------
     [WARNING]: Failure using method (v2_runner_on_unreachable) in callback plugin
    (<testinfra.utils.ansible_runner.Callback object at 0x7efccb1c7350>): Host
    molecule-test-bionic is unreachable: {'changed': False,  'msg':
    u'container not found: molecule-test-bionic',  'unreachable': True}

The traceback itself is not very helpful (KeyError?), and only the captured stderr points to the problem. This may not be captured if you run with -s. Maybe it could check earlier for whether the host is reachable and fail there with an appropriate message?

[philpep]

Yes, I think we could catch the {'unreachable': True} in the ansible result and display appropriate message.