Make settings machinery support Pulp 3

When applied, this commit will redefine what a "valid" configuration
file is. Existing configuration files will continue to be valid. But in
addition, entirely new (and similar-looking) configuration files may
also be written.

The old configuration files are suitable for use when testing Pulp 2.
They let one declare information like "host pulp.example.com is running
rabbitmq." The new configuration files are suitable for testing Pulp 3.
They lew one declare information like "host pulp.example.com is running
redis."

In addition, this commit will update two pieces of machinery that are
related to the configuration file. Specifically, this commit will
overhaul the entire CLI interface (as accessed by the `pulp-smash`
executable) and re-implement the `PulpSmashConfig.get_services` method.

Fix: #965

Fix: #980

docs/usage.rst

@@ -89,7 +89,8 @@ you declare properties of the individual hosts that comprise the Pulp
 application.
 
 Each host must fulfill the "shell" role. In addition, the hosts must
-collectively fulfill the :obj:`pulp_smash.config.REQUIRED_ROLES`.
+collectively fulfill either :obj:`pulp_smash.config.P2_REQUIRED_ROLES` or
+:obj:`pulp_smash.config.P3_REQUIRED_ROLES`.
 
 Not all roles requires additional information. Currently, only the ``amqp
 broker``, ``api`` and ``shell`` roles do. The ``amqp broker`` object must have a

pulp_smash/cli.py

@@ -7,6 +7,7 @@
 from urllib.parse import urlsplit
 
 import plumbum
+from packaging.version import Version
 
 from pulp_smash import exceptions
 
@@ -176,8 +177,10 @@ class Client():  # pylint:disable=too-few-public-methods
         the host on which commands will be executed.
     :param response_handler: A callback function. Defaults to
         :func:`pulp_smash.cli.code_handler`.
-    :param pulp_smash.config.PulpHost pulp_host: A specific host to target,
-        instead of the first host with the ``pulp cli`` role.
+    :param pulp_smash.config.PulpHost pulp_host: A specific host to target.
+        Defaults to the first host with the ``pulp cli`` role when targeting
+        Pulp 2, and the first host with the ``shell`` role when targeting Pulp
+        3. If Pulp 3 gets a CLI, this latter default may change.
 
     .. _Plumbum: http://plumbum.readthedocs.io/en/latest/index.html
     """
@@ -186,7 +189,10 @@ def __init__(self, cfg, response_handler=None, pulp_host=None):
         """Initialize this object with needed instance attributes."""
         # How do we make requests?
         if not pulp_host:
-            pulp_host = cfg.get_hosts('pulp cli')[0]
+            if cfg.pulp_version < Version('3'):
+                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')
@@ -510,7 +516,7 @@ class ServiceManager(BaseServiceManager):
 
     >>> from pulp_smash import cli, config
     >>> cfg = config.get_config()
-    >>> pulp_host = cfg.get_get_services(('api',))[0]
+    >>> pulp_host = cfg.get_services(('api',))[0]
     >>> svc_mgr = cli.ServiceManager(cfg, pulp_host)
     >>> completed_process_list = svc_mgr.stop(['httpd'])
     >>> completed_process_list = svc_mgr.start(['httpd'])