Merge ~cjwatson/launchpad:py3-limitedlist into launchpad:master

[Colin Watson]

Fix LimitedList for Python 3

The slice protocol is a bit different, as is one exception message.

[Thiago F. Pappacena (pappacena)]

LGTM

review: Approve

diff --git a/lib/lp/services/doc/limitedlist.txt b/lib/lp/services/doc/limitedlist.txt
index 4abd0a0..10f1fed 100644
--- a/lib/lp/services/doc/limitedlist.txt
+++ b/lib/lp/services/doc/limitedlist.txt
@@ -16,7 +16,7 @@ The property max_length stores the maximum allowed length of the list.
     >>> LimitedList()
     Traceback (most recent call last):
     ...
-    TypeError: __new__() takes at least 2 arguments (1 given)
+    TypeError: __new__() ...
 
 We can optionally specify the initial content of the sequence. Note that
 only the last N elements of the second parameter are stored, where N is
diff --git a/lib/lp/services/limitedlist.py b/lib/lp/services/limitedlist.py
index 5033df7..ea340b9 100644
--- a/lib/lp/services/limitedlist.py
+++ b/lib/lp/services/limitedlist.py
@@ -30,7 +30,7 @@ class LimitedList(list):
         """Ensure that the maximum length is not exceeded."""
         elements_to_drop = self.__len__() - self.max_length
         if elements_to_drop > 0:
-            self.__delslice__(0, elements_to_drop)
+            del self[0:elements_to_drop]
 
     def __add__(self, other):
         return LimitedList(
@@ -56,6 +56,12 @@ class LimitedList(list):
         self._ensureLength()
         return result
 
+    def __setitem__(self, key, value):
+        result = super(LimitedList, self).__setitem__(key, value)
+        if isinstance(key, slice):
+            self._ensureLength()
+        return result
+
     def __setslice__(self, i, j, sequence):
         result = super(LimitedList, self).__setslice__(i, j, sequence)
         self._ensureLength()