fix state issue

kindlecomicconverter/comic2ebook.py

@@ -627,7 +627,7 @@ def getWorkFolder(afile):
                 path = cbx.extract(workdir)
             except OSError as e:
                 rmtree(workdir, True)
-                raise UserWarning(e.strerror)
+                raise UserWarning(e)
     else:
         raise UserWarning("Failed to open source file/directory.")
     sanitizePermissions(path)