Hi!
I'm using sage 9.6 on Fedora 36, installed via dnf. I am seeing the following. The version of nauty package that I see installed is nauty-2.7.4-1.fc36.x86_64.
```
sage: for t in digraphs.tournaments_nauty(6):
....: print(t)
....:
---------------------------------------------------------------------------
FeatureNotPresentError Traceback (most recent call last)
Input In [1], in <cell line: 1>()
----> 1 for t in digraphs.tournaments_nauty(Integer(6)):
2 print(t)
File /usr/lib64/python3.10/site-packages/sage/graphs/digraph_generators.py:532, in DiGraphGenerators.tournaments_nauty(self, n, min_out_degree, max_out_degree, strongly_connected, debug, options)
530 import shlex
531 from sage.features.nauty import NautyExecutable
--> 532 gentourng_path = NautyExecutable("gentourng").absolute_filename()
534 sp = subprocess.Popen(shlex.quote(gentourng_path) + " {0}".format(nauty_input),
535 shell=True,
536 stdin=subprocess.PIPE, stdout=subprocess.PIPE,
537 stderr=subprocess.PIPE, close_fds=True)
539 if debug:
File /usr/lib64/python3.10/site-packages/sage/features/__init__.py:619, in Executable.absolute_filename(self)
617 if path is not None:
618 return path
--> 619 raise FeatureNotPresentError(self,
620 reason="Executable {executable!r} not found on PATH.".format(executable=self.executable),
621 resolution=self.resolution())
FeatureNotPresentError: nauty_gentourng is not available.
Executable 'gentourng' not found on PATH.
No equivalent system packages for pip are known to Sage.
```
It seems like no generators based on nauty are available, as I get the same error with `geng` if I want to access items from `graphs.nauty_geng("2")`.
If I recall correctly, there were no additional (installation) steps needed for these things to work in e.g. Sage 8.3. And I can't find any notes about this afterwards. Any help is much appreciated!
Thanks in advance,
Jakub