print(binascii.hexlify(b" a nice nice long string"))
you can find both the string in your listing
0x0000000000000714 <+26>: movabs rax,...
You don't need to make install the binary, this often strips the binary removing all the debug information.
In the HACKING file these is a section on how to debug this tool, they advise the following settings, personally I would add -ggdb to enable gdb specific bindings. (This advice also applies to other projects, although this project has explicitly added ...