redfam: Add method to check disc section

Sometimes disc sections are disapering since the heading is changed
and the famhash changes, so we get a new redfam. Mark those as absent

Issue #64 (https://git.golderweb.de/wiki/jogobot-red/issues/64)

lib/redfam.py

@@ -366,6 +366,9 @@ class RedFamParser( RedFam ):
         - 3 and greater status was set by worker script, do not change it
         """
 
+        # Since we have parsed it, the section can never be absent
+        self.status.remove("absent")
+
         # No ending, discussion is running:
         # Sometimes archived discussions also have no detectable ending
         if not self.ending and not self.redpage.archive:
@@ -674,6 +677,36 @@ class RedFamWorker( RedFam ):
         # We try it without any more parsing as mw will do while parsing page
         return ( self.redpage.pagetitle + "#" + anchor_code.strip() )
 
+    def disc_section_exists( self ):
+        """
+        Checks weather the redundance discussion is still existing. Sometimes
+        it is absent, since heading was changed and therefore we get a
+        different famhash ergo new redfam.
+        As a side effect, the method sets status "absent" for missing sections.
+
+        @returns True if it exists otherwise False
+        @rtype bool
+        """
+        # The redpage
+        discpage = pywikibot.Page(pywikibot.Site(), self.get_disc_link() )
+
+        # Parse redpage content
+        wikicode = mwparser.parse( discpage.get() )
+
+        # List fams
+        fams = wikicode.filter_headings(
+            matches=RedFamParser.is_section_redfam_cb )
+
+        # Check if current fam is in list of fams
+        # If not, set status absent and return False
+        if self.heading not in [ fam.title.strip() for fam in fams]:
+            self.status.remove("open")
+            self.status.add("absent")
+            return False
+
+        # The section exists
+        return True
+
     def generate_disc_notice_template( self ):
         """
         Generates notice template to add on discussion Pages of Articles when