Turn iterables into lists for in operator.

The implementation is currently written in a way that would try
to consume the iterator multiple times and cannot deal with new
memoryviews like those returned by dict.keys().

src/DocumentTemplate/DT_In.py

@@ -465,6 +465,11 @@ def renderwb(self, md):
             raise ValueError(
                 'Strings are not allowed as input to the in tag.')
 
+        # Turn iterable like dict.keys() into a list.
+        sequence = list(sequence)
+        if cache is not None:
+            cache[name] = sequence
+
         section = self.section
         params = self.args
 
@@ -668,6 +673,11 @@ def renderwob(self, md):
             raise ValueError(
                 'Strings are not allowed as input to the in tag.')
 
+        # Turn iterable like dict.keys() into a list.
+        sequence = list(sequence)
+        if cache is not None:
+            cache[name] = sequence
+
         section = self.section
         mapping = self.mapping
         no_push_item = self.no_push_item

src/DocumentTemplate/DT_InSV.py

@@ -31,6 +31,9 @@ class sequence_variables(object):
 
     def __init__(self, items=None, query_string='', start_name_re=None,
                  alt_prefix=''):
+        if items is not None:
+            # Turn iterable into a list, to support key lookup
+            items = list(items)
         self.items = items
         self.query_string = query_string
         self.start_name_re = start_name_re