code: def registerErrorHandler(f, ctx):
      
      import sys
      if 'libxslt' not in sys.modules:
          # normal behaviour when libxslt is not imported
          ret = libxml2mod.xmlRegisterErrorHandler(f,ctx)
      else:
          # when libxslt is already imported, one must
          # use libxst's error handler instead
          import libxslt
          ret = libxslt.registerErrorHandler(f,ctx)
      return ret
docs: Register a Python written function to for error reporting.
         The function is called back as f(ctx, error).