A guess here, but this was probably the cause of a previous FTBFS in augur [1].
[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1058394
- Bug#1088355: pyfastx: missing versioned depende... Graham Inggs
- Bug#1088355: pyfastx: missing versioned de... Graham Inggs
- Processed: Bug#1088355 marked as pending i... Debian Bug Tracking System
- Bug#1088355: marked as pending in pyfastx Étienne Mollier
- Bug#1088355: marked as done (pyfastx: miss... Debian Bug Tracking System
