Add installation instruction file;

Order directories.

rivista/xml/opml.py

@@ -0,0 +1,32 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+import datetime
+from rivista.xmpp.utilities import XmppUtilities
+import xml.etree.ElementTree as ET
+
+class XmlOpml:
+
+    def generate_opml(iq):
+        """Generate an OPML Collection document."""
+        pubsub = iq['from'].bare
+        items = iq['disco_items']['items']
+        opml = ET.Element("opml")
+        opml.set("version", "1.0")
+        head = ET.SubElement(opml, "head")
+        ET.SubElement(head, "title").text = 'An OPML of ' + pubsub
+        ET.SubElement(head, "description").text = (
+            "PubSub Nodes of {}").format(pubsub)
+        ET.SubElement(head, "generator").text = 'Rivista'
+        ET.SubElement(head, "urlPublic").text = 'https://git.xmpp-it.net/sch/Rivista'
+        time_stamp = datetime.datetime.now(datetime.UTC).isoformat()
+        ET.SubElement(head, "dateCreated").text = time_stamp
+        ET.SubElement(head, "dateModified").text = time_stamp
+        body = ET.SubElement(opml, "body")
+        for item in items:
+            pubsub, node, title = item
+            uri = XmppUtilities.form_a_node_link(pubsub, node)
+            outline = ET.SubElement(body, "outline")
+            outline.set("text", title or node)
+            outline.set("xmlUrl", uri)
+        return ET.tostring(opml, encoding='unicode')