Do not break when reindexing multiple indexes (#89)

CHANGES.rst

@@ -4,7 +4,9 @@ Changelog
 5.1 (unreleased)
 ----------------
 
-- Nothing changed yet.
+- Fix exception happening when reindexing multiple indexes while having a
+  progress handler.
+  (`#89 <https://github.com/zopefoundation/Products.ZCatalog/pull/89>`_)
 
 
 5.0.1 (2019-06-17)

src/Products/ZCatalog/ZCatalog.py

@@ -410,14 +410,14 @@ def manage_clearIndex(self, ids=None,
 
     @security.protected(manage_zcatalog_entries)
     def reindexIndex(self, name, REQUEST, pghandler=None):
-        if isinstance(name, str):
-            name = (name, )
-
+        # This method does the actual reindexing of indexes.
+        # `name` can be the name of an index of a list of names.
+        idxs = (name, ) if isinstance(name, str) else name
         paths = self._catalog.uids.keys()
 
         i = 0
         if pghandler:
-            pghandler.init('reindexing %s' % name, len(paths))
+            pghandler.init('reindexing {}'.format(idxs), len(paths))
 
         for p in paths:
             i += 1
@@ -433,7 +433,7 @@ def reindexIndex(self, name, REQUEST, pghandler=None):
             else:
                 # don't update metadata when only reindexing a single
                 # index via the UI
-                self.catalog_object(obj, p, idxs=name,
+                self.catalog_object(obj, p, idxs=idxs,
                                     update_metadata=0, pghandler=pghandler)
 
         if pghandler: