build errors on Fedora 24 and CentOS 7

[Lukas Pirl]

On 10/12/2016 12:49 AM, Brian Warner wrote as excerpted:
> Or maybe there's something funny with the regexp? Different newline
> convention on that box? Some unicode thing?
> 
> I guess the next step is to modify the tests to log the full output from
> /bin/ip to test.log, or maybe add a separate buildstep to do the same.

Well, after a few minutes stepping around, pdb told me the reason for
this failure. It was quite trivial in the end: the path to `ip` is just
different on RHEL-based systems.

I filed a PR¹ accordingly.

Nevertheless, I guess
  allmydata.test.test_magic_folder.RealTest.test_move_tree
will continue to fail. Let's see.

Best,

Lukas

¹ https://github.com/tahoe-lafs/tahoe-lafs/pull/364 accord