Started work on cleaning up how exceptions are caught and sys.exit() is called in ipalib.cli.CLI

ipalib/errors.py

@@ -98,6 +98,7 @@ class IPAError(StandardError):
     """
 
     format = None
+    faultCode = 1
 
     def __init__(self, *args):
         self.args = args
@@ -109,6 +110,16 @@ class IPAError(StandardError):
         return self.format % self.args
 
 
+class InvocationError(IPAError):
+    pass
+
+class UnknownCommandError(InvocationError):
+    format = 'unknown command "%s"'
+
+class UnknownHelpError(InvocationError):
+    format = 'no command nor topic "%s"'
+
+
 class ArgumentError(IPAError):
     """
     Raised when a command is called with wrong number of arguments.