don't know a whole much about python but,
would it be better to return None on error, instead of a tuple containing Nones?

using it to have a linespec enabled disas command, similar to:
python
x = gdb.decode_line("test.c:14")[1][0].find_line_pc_range();
gdb.execute("disassemble " + str(x[0]) + "," + str(x[1]))
end

2011-07-01  Matt Rice  <ratmice@gmail.com>

        * python/py-symtab.c: Populate sal_object_methods.
        (salpy_find_line_pc_range): New function.

2011-07-01  Matt Rice  <ratmice@gmail.com>

        * gdb.texinfo (Symbol Tables In Python): Add find_line_pc_range method.