[MacPorts] #56389: rrdtool @1.7.0: fix missing dependency for dejavu-fonts

[macports at parvis.nl]

> On 2018-05-01, at 22:56, MacPorts <noreply at macports.org> wrote:
> (...)
> Tidy other deps based on port-depcheck.sh analysis

- what is that?
- can I do that myself?