install: fix command line option validation

The code which calls the validators was accidentally removed, re-add it.

https://fedorahosted.org/freeipa/ticket/5386
https://fedorahosted.org/freeipa/ticket/5391
https://fedorahosted.org/freeipa/ticket/5392

Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>

ipapython/install/cli.py

@@ -282,7 +282,8 @@ class ConfigureTool(admintool.AdminTool):
         kwargs = {}
 
         transformed_cls = self._transform(self.configurable_class)
-        for owner_cls, name in transformed_cls.knobs():
+        knob_classes = {n: getattr(c, n) for c, n in transformed_cls.knobs()}
+        for name in knob_classes:
             value = getattr(self.options, name, None)
             if value is not None:
                 kwargs[name] = value
@@ -294,8 +295,10 @@ class ConfigureTool(admintool.AdminTool):
         try:
             cfgr = transformed_cls(**kwargs)
         except core.KnobValueError as e:
-            knob_cls = getattr(transformed_cls, e.name)
+            knob_cls = knob_classes[e.name]
             try:
+                if self.positional_arguments is None:
+                    raise IndexError
                 index = self.positional_arguments.index(e.name)
             except IndexError:
                 cli_name = knob_cls.cli_name or e.name.replace('_', '-')