Adding note about url needing to be encoded when provided to the urlopen function as well as the Request class.

Author: mblahay

Doc/library/urllib.request.rst

@@ -28,8 +28,8 @@ The :mod:`urllib.request` module defines the following functions:
 
 .. function:: urlopen(url, data=None[, timeout], *, cafile=None, capath=None, cadefault=False, context=None)
 
-   Open the URL *url*, which can be either a string or a
-   :class:`Request` object.
+   Open *url*, which can be either a string containing a valid, properly
+   encoded, URL or a :class:`Request` object.
 
    *data* must be an object specifying additional data to be sent to the
    server, or ``None`` if no such data is needed.  See :class:`Request`
@@ -192,7 +192,7 @@ The following classes are provided:
 
    This class is an abstraction of a URL request.
 
-   *url* should be a string containing a valid URL.
+   *url* should be a string containing a valid, properly encoded, URL.
 
    *data* must be an object specifying additional data to send to the
    server, or ``None`` if no such data is needed.  Currently HTTP