Add API version and have server reject incompatible clients.

This patch contains 2 parts.

The first part is a small utility to create and validate the current
API. To do this it needs to load ipalib which on a fresh system
introduces a few problems, namely that it relies on a python plugin
to set the default encoding to utf8. For our purposes we can skip that.
It is also important that any optional plugins be loadable so the
API can be examined.

The second part is a version exchange between the client and server.
The version has a major and a minor version. The major verion is
updated whenever existing API changes. The minor version is updated when
new API is added. A request will be rejected if either the major versions
don't match or if the client major version is higher than then server
major version (though by implication new API would return a command not
found if allowed to proceed).

To determine the API version of the server from a client use the ping
command.

ticket 584

ipalib/cli.py

@@ -32,7 +32,14 @@ import fcntl
 import termios
 import struct
 import base64
-import default_encoding_utf8
+try:
+    import default_encoding_utf8
+except ImportError:
+    # This is a chicken-and-egg problem. The api can't be imported unless
+    # this is already installed and since it is installed with IPA therein
+    # lies the problem. Skip it for now so ipalib can be imported in-tree
+    # even in cases that IPA isn't installed on the dev machine.
+    pass
 
 import frontend
 import backend
@@ -42,6 +49,7 @@ from errors import PublicError, CommandError, HelpError, InternalError, NoSuchNa
 from constants import CLI_TAB
 from parameters import Password, Bytes, File
 from text import _
+from ipapython.version import API_VERSION
 
 
 def to_cli(name):
@@ -884,6 +892,7 @@ class cli(backend.Executioner):
         if not isinstance(cmd, frontend.Local):
             self.create_context()
         kw = self.parse(cmd, argv)
+        kw['version'] = API_VERSION
         if self.env.interactive:
             self.prompt_interactively(cmd, kw)
         self.load_files(cmd, kw)
@@ -931,6 +940,8 @@ class cli(backend.Executioner):
                 dest=option.name,
                 help=unicode(option.doc),
             )
+            if 'no_option' in option.flags:
+                continue
             if option.password and self.env.interactive:
                 kw['action'] = 'store_true'
             elif option.type is bool and option.autofill: