Lazy load the cli.Client machine

Problem:

Everytime we instantiate a new instance of `cli.Client` its `__init__` method
code tries to make communication with the remote host to determine if it is
a local or ssh machine to be used.

The communication with `machine` should be done only when it is necessary,
which is when the `run` command is called.

Solution:

Transform `machine` in a lazy `@property` then it is instantiated only
when it is first called.

pulp_smash/cli.py

@@ -193,26 +193,30 @@ def __init__(self, cfg, response_handler=None, pulp_host=None):
                 pulp_host = cfg.get_hosts("pulp cli")[0]
             else:
                 pulp_host = cfg.get_hosts("shell")[0]
-        self.pulp_host = pulp_host
-        hostname = pulp_host.hostname
-        transport = pulp_host.roles.get("shell", {}).get("transport")
-        if transport is None:
-            transport = "local" if hostname == socket.getfqdn() else "ssh"
-        if transport == "local":
-            self.machine = plumbum.machines.local
-        else:  # transport == 'ssh'
-            # The SshMachine is a wrapper around the host's "ssh" binary.
-            # Thus, it uses ~/.ssh/config, ~/.ssh/known_hosts, etc.
-            self.machine = plumbum.machines.SshMachine(hostname)
-
-        # How do we handle responses?
-        if response_handler is None:
-            self.response_handler = code_handler
-        else:
-            self.response_handler = response_handler
 
+        self.pulp_host = pulp_host
+        self.response_handler = response_handler or code_handler
         self.cfg = cfg
+
         self._is_root_cache = None
+        self._machine = None
+
+    @property
+    def machine(self):
+        """Initialize the plumbum machine lazily."""
+        if self._machine is None:
+            hostname = self.pulp_host.hostname
+            transport = self.pulp_host.roles.get("shell", {}).get("transport")
+            if transport is None:
+                transport = "local" if hostname == socket.getfqdn() else "ssh"
+
+            if transport == "local":
+                self._machine = plumbum.machines.local
+            else:  # transport == 'ssh'
+                # The SshMachine is a wrapper around the host's "ssh" binary.
+                # Thus, it uses ~/.ssh/config, ~/.ssh/known_hosts, etc.
+                self._machine = plumbum.machines.SshMachine(hostname)
+        return self._machine
 
     @property
     def is_superuser(self):

tests/test_cli.py

@@ -180,7 +180,7 @@ def test_run(self):
             ]
         )
         client = cli.Client(cfg)
-        with mock.patch.object(client, "machine") as machine:
+        with mock.patch.object(client, "_machine") as machine:
 
             machine.__getitem__.return_value = machine
             machine.run.return_value = (0, "ok", None)
@@ -205,7 +205,7 @@ def test_run_as_sudo(self):
             ]
         )
         client = cli.Client(cfg)
-        with mock.patch.object(client, "machine") as machine:
+        with mock.patch.object(client, "_machine") as machine:
 
             machine.__getitem__.return_value = machine
             machine.run.return_value = (0, "ok", None)