gh-151943: Fix Sphinx reference warnings in Doc/library/xmlrpc.client.rst

Error, the base class of Fault and ProtocolError, and the Server alias
of ServerProxy are public but had no entries, so references to them did
not resolve. Document them next to ServerProxy; the alias note moves out
of the ServerProxy description into the new Server entry. Transport and
SafeTransport are described as internal and are left undocumented, as
the note at the top of the file says, so those links are suppressed, as
is the link to the ServerProxy.system attribute, which has no entry of
its own; the methods under it are documented as
ServerProxy.system.listMethods() and so on.

Doc/library/xmlrpc.client.rst now builds clean in nit-picky mode and
comes out of Doc/tools/.nitignore.

Author: jang-hs

Doc/library/xmlrpc.client.rst

@@ -39,8 +39,8 @@ between conformable Python objects and XML on the wire.
    remote XML-RPC server.  The required first argument is a URI (Uniform Resource
    Indicator), and will normally be the URL of the server.  The optional second
    argument is a transport factory instance; by default it is an internal
-   :class:`SafeTransport` instance for https: URLs and an internal HTTP
-   :class:`Transport` instance otherwise.  The optional third argument is an
+   :class:`!SafeTransport` instance for https: URLs and an internal HTTP
+   :class:`!Transport` instance otherwise.  The optional third argument is an
    encoding, by default UTF-8. The optional fourth argument is a debugging flag.
 
    The following parameters govern the use of the returned proxy instance.
@@ -142,9 +142,6 @@ between conformable Python objects and XML on the wire.
    via XML-RPC, use :class:`bytes` or :class:`bytearray` classes or the
    :class:`Binary` wrapper class described below.
 
-   :class:`Server` is retained as an alias for :class:`ServerProxy` for backwards
-   compatibility.  New code should use :class:`ServerProxy`.
-
    .. versionchanged:: 3.5
       Added the *context* argument.
 
@@ -156,6 +153,17 @@ between conformable Python objects and XML on the wire.
       See https://ws.apache.org/xmlrpc/types.html for a description.
 
 
+.. class:: Server
+
+   Retained as an alias for :class:`ServerProxy` for backwards compatibility.
+   New code should use :class:`ServerProxy`.
+
+
+.. exception:: Error
+
+   Base class of the :exc:`Fault` and :exc:`ProtocolError` exceptions.
+
+
 .. seealso::
 
    `XML-RPC HOWTO <https://tldp.org/HOWTO/XML-RPC-HOWTO/index.html>`_
@@ -181,7 +189,7 @@ by returning data in a conformant type or by raising a :class:`Fault` or
 :class:`ProtocolError` exception indicating an error.
 
 Servers that support the XML introspection API support some common methods
-grouped under the reserved :attr:`~ServerProxy.system` attribute:
+grouped under the reserved :attr:`!system` attribute:
 
 
 .. method:: ServerProxy.system.listMethods()

Doc/tools/.nitignore

@@ -24,5 +24,4 @@ Doc/library/wsgiref.rst
 Doc/library/xml.dom.minidom.rst
 Doc/library/xml.sax.reader.rst
 Doc/library/xml.sax.rst
-Doc/library/xmlrpc.client.rst
 Doc/library/xmlrpc.server.rst