completion: get rid of model-specific sort method (see #545)

qutebrowser/completion/models/base.py

@@ -126,10 +126,3 @@ class BaseCompletionModel(QStandardItemModel):
         else:
             # category
             return Qt.NoItemFlags
-
-    def sort(self, column, order=Qt.AscendingOrder):
-        """Sort the data in column according to order.
-
-        Override QAbstractItemModel::sort.
-        """
-        raise NotImplementedError

qutebrowser/completion/models/sortfilter.py

@@ -63,9 +63,6 @@ class CompletionFilterModel(QSortFilterProxyModel):
 
         Invalidates the filter and re-sorts the model.
 
-        If the current completion model overrides sort(), it is used.
-        If not, the default implementation in QCompletionFilterModel is called.
-
         Args:
             val: The value to set.
         """
@@ -76,10 +73,7 @@ class CompletionFilterModel(QSortFilterProxyModel):
             self.pattern_re = re.compile(val, re.IGNORECASE)
             self.invalidateFilter()
             sortcol = 0
-            try:
-                self.srcmodel.sort(sortcol)
-            except NotImplementedError:
-                self.sort(sortcol)
+            self.sort(sortcol)
             self.invalidate()
 
     def count(self):