https://sourceforge.net/p/pyfltk/code/506/

--- a/swig/filename.i
+++ b/swig/filename.i
@@ -14,6 +14,7 @@
 %ignore fl_alphasort;
 %ignore fl_casealphasort;
 %ignore fl_casenumericsort;
+%ignore _fl_filename_isdir_quick;
 
 %include "FL/filename.H"