No traceback for non-existent items in history

Author: schlatterbeck

CHANGES.txt

@@ -45,6 +45,8 @@ Fixed:
   Meerwald)
 - issue2550994: avoid breakage caused by use of backports of Python 3
   configparser module to Python 2. (Joseph Myers)
+- Make non-existent items in history not cause a traceback (Ralf
+  Schlatterbeck)
 
 
 2018-07-13 1.6.0

roundup/hyperdb.py

@@ -1101,6 +1101,13 @@ def history(self, nodeid, enforceperm=True, skipquiet=True):
                         if not enforceperm or allow_obsolete:
                             journal.append(j)
                         continue
+                    # obsolete linked-to item
+                    try:
+                        k = cls.get (linkid, key)
+                    except IndexError:
+                        if not enforceperm or allow_obsolete:
+                            journal.append(j)
+                        continue
                     # is the updated property quiet?
                     if skipquiet and cls.properties[key].quiet:
                         logger.debug("skipping quiet property: "