The class is called LineTable, not Linetable, as specified by
py-linetable.c/gdbpy_initialize_linetable:
if (gdb_pymodule_addobject (gdb_module, "LineTable",
gdb/ChangeLog:
* python/py-linetable.c: Fix case of Linetable to LineTable
in docstrings and code comments.
* python/py-symtab.c: Same.