Merge branch '2.0'

doc/extdev/deprecated.rst

@@ -26,6 +26,16 @@ The following is a list of deprecated interfaces.
      - (will be) Removed
      - Alternatives
 
+   * - ``sphinx.io.FiletypeNotFoundError``
+     - 2.4
+     - 4.0
+     - ``sphinx.errors.FiletypeNotFoundError``
+
+   * - ``sphinx.io.get_filetype()``
+     - 2.4
+     - 4.0
+     - ``sphinx.util.get_filetype()``
+
    * - ``sphinx.builders.gettext.POHEADER``
      - 2.3
      - 4.0