issue2193 - Update docs about the legal characters allowed in Cookie name

Doc/library/http.cookies.rst

@@ -17,8 +17,17 @@ cookie value.
 
 The module formerly strictly applied the parsing rules described in the
 :rfc:`2109` and :rfc:`2068` specifications.  It has since been discovered that
-MSIE 3.0x doesn't follow the character rules outlined in those specs.  As a
-result, the parsing rules used are a bit less strict.
+MSIE 3.0x doesn't follow the character rules outlined in those specs and also
+many current day browsers and servers have relaxed parsing rules when comes to
+Cookie handling.  As a result, the parsing rules used are a bit less strict.
+
+The character set, :data:`string.ascii_letters`, :data:`string.digits` and
+``!#$%&'*+-.^_`|~:`` denote the set of valid characters allowed by this module
+in Cookie name (as :attr:`~Morsel.key`).
+
+.. versionchanged:: 3.3
+   Allowed ':' as a valid Cookie name character.
+
 
 .. note::