Improve #19204: Improved cross-references in the urllib package documentation.

diff --cc Doc/library/urllib.error.rst
index 7bd04b1bc466da44ae9fcfe9ceb582e9d9d02efc,25c13bdc32e886e1c435a24dcadfa5317b5acdeb..9fb58f5083587864030c0fd2a6cc8657e685cc07
--- 1/Doc/library/urllib.error.rst
--- 2/Doc/library/urllib.error.rst
+++ b/Doc/library/urllib.error.rst
@@@ -45,16 -46,10 +46,17 @@@ The following exceptions are raised by 
  
        This is usually a string explaining the reason for this error.
  
 +   .. attribute:: headers
 +
 +      The HTTP response headers for the HTTP request that cause the
 +      :exc:`HTTPError`.
 +
 +      .. versionadded:: 3.4
 +
  .. exception:: ContentTooShortError(msg, content)
  
-    This exception is raised when the :func:`urlretrieve` function detects that
+    This exception is raised when the :func:`~urllib.request.urlretrieve`
+    function detects that
     the amount of the downloaded data is less than the expected amount (given by
     the *Content-Length* header).  The :attr:`content` attribute stores the
     downloaded (and supposedly truncated) data.

diff --cc Doc/library/urllib.request.rst
index ef902b1137b46640d1e29eb667a7d6607e77d5e3,eac222f87bc44b21899b48d7435619bb39993fcc..61b77349551267642bbd4a40347bf3192905c2b9
--- 1/Doc/library/urllib.request.rst
--- 2/Doc/library/urllib.request.rst
+++ b/Doc/library/urllib.request.rst
@@@ -947,24 -980,9 +948,24 @@@ FileHandler Object
  
     .. versionchanged:: 3.2
        This method is applicable only for local hostnames.  When a remote
-       hostname is given, an :exc:`URLError` is raised.
+       hostname is given, an :exc:`~urllib.error.URLError` is raised.
  
  
 +.. _data-handler-objects:
 +
 +DataHandler Objects
 +-------------------
 +
 +.. method:: DataHandler.data_open(req)
 +
 +   Read a data URL. This kind of URL contains the content encoded in the URL
 +   itself. The data URL syntax is specified in :rfc:`2397`. This implementation
 +   ignores white spaces in base64 encoded data URLs so the URL may be wrapped
 +   in whatever source file it comes from. But even though some browsers don't
 +   mind about a missing padding at the end of a base64 encoded data URL, this
 +   implementation will raise an :exc:`ValueError` in that case.
 +
 +
  .. _ftp-handler-objects:
  
  FTPHandler Objects