PEP 566: Updates (#574)

* PEP 566: Change to .rst extension

* PEP 566: Allow description in message body

pep-0566.rst

@@ -81,6 +81,14 @@ Name
 The specification for the format of this field is now identical to the
 distribution name specification defined in PEP 508.
 
+Description
+:::::::::::
+
+In addition to the ``Description`` header field, the distribution's
+description may instead be provided in the message body (i.e., after a
+completely blank line following the headers, with no indentation or other
+special formatting necessary).
+
 Version Specifiers
 ==================
 
@@ -124,6 +132,8 @@ as follows:
    single list containing all the original values for the given key;
 #. The ``Keywords`` field should be converted to a list by splitting the
    original value on whitespace characters;
+#. The message body, if present, should be set to the value of the
+   ``description`` key.
 #. The result should be stored as a string-keyed dictionary.
 
 Summary of Differences From PEP 345