FFTW warnings in Travis



These are only warnings, but I was wondering if anyone has a remedy for this, or should I just ignore it:

WARNING: --output requested, but no modules defined during run
WARNING: The call to compilecache failed to create a usable precompiled cache file for module FFTW. Got:
WARNING: Cache file "/home/travis/.julia/lib/v0.6/FFTW.ji" not found.
WARNING: eval from module Main to ImageCore:    
Expr(:call, Expr(:., :Base, :include_from_node1)::Any, "/home/travis/.julia/v0.6/FFTW/src/FFTW.jl")::Any
  ** incremental compilation may be broken for this module **


I think it’s unharmful, you can just ignore it.