Bug#942393: mlpack: downloads stuff from internet during build?

[Gianfranco Costamagna]

Source: mlpack
Version: 3.2.1-1
Severity: serious

Hello, according to the build log:
-- Found Armadillo: /usr/lib/libarmadillo.so (found suitable version "9.600.5", minimum required is "8.400.0") 
-- Armadillo libraries: /usr/lib/libarmadillo.so
-- Could NOT find STB_IMAGE (missing: STB_IMAGE_INCLUDE_DIR) 
-- [download 3% complete]
-- [download 5% complete]
-- [download 10% complete]
-- [download 16% complete]
-- [download 18% complete]
-- [download 20% complete]
-- [download 24% complete]
-- [download 30% complete]
-- [download 31% complete]
-- [download 36% complete]
-- [download 37% complete]
-- [download 39% complete]
-- [download 44% complete]
-- [download 50% complete]
-- [download 54% complete]
-- [download 60% complete]
-- [download 64% complete]
-- [download 65% complete]
-- [download 67% complete]
-- [download 70% complete]
-- [download 72% complete]
-- [download 75% complete]
-- [download 77% complete]
-- [download 78% complete]
-- [download 80% complete]
-- [download 83% complete]
-- [download 84% complete]
-- [download 90% complete]
-- [download 96% complete]
-- [download 98% complete]
-- [download 99% complete]
-- [download 100% complete]
-- [download 20% complete]
-- [download 30% complete]
-- [download 49% complete]
-- [download 53% complete]
-- [download 61% complete]
-- [download 74% complete]
-- [download 86% complete]
-- [download 90% complete]
-- [download 98% complete]
-- [download 100% complete]
-- Successfully downloaded stb into /<<PKGBUILDDIR>>/obj-x86_64-linux-gnu/deps/stb/
-- Found Ensmallen: /usr/include (found suitable version "2.10.3", minimum required is "2.10.0") 
-- Boost version: 1.67.0
-- Found the following Boost libraries:
--   program_options
--   unit_test_framework
--   serialization
-- Found OpenMP_C: -fopenmp (found version "4.5") 
-- Found OpenMP_CXX: -fopenmp (found version "4.5") 
-- Found OpenMP: TRUE (found version "4.5")  


I discovered this in Ubuntu build logs, because there internet connection is more strictly forbidden, but this seems to be happening in Debian in the very same way, just not fatal for builders

Gianfranco