LaunchPad recipe failing: curl error: Could not resolve host: github.com

[Jonathan Thomas]

Greetings! I am trying to get a recipe building on LaunchPad which happens to be a rust library, built with cargo. During the build, cargo downloads some things from GitHub, to compile certain dependencies, which does not seem to work on the LaunchPad builders. Here is the buildlog and a snippet of the error:
https://launchpadlibrarian.net/406654570/buildlog_ubuntu-xenial-amd64.resvg_0.5.0+341+201901180003+daily~ubuntu16.04.1_BUILDING.txt.gz

dh build
   dh_testdir
   dh_update_autotools_config
   dh_auto_configure
   debian/rules override_dh_auto_build
make[1]: Entering directory '/<<BUILDDIR>>/resvg-0.5.0+341+201901180003+daily~ubuntu16.04.1'
CARGO_HOME='/<<BUILDDIR>>/resvg-0.5.0+341+201901180003+daily~ubuntu16.04.1/.cargo/' cargo build --verbose --release --features="qt-backend" --manifest-path=capi/Cargo.toml;
    Updating crates.io index
warning: spurious network error (2 tries remaining): curl error: Could not resolve host: github.com
; class=Net (12)
warning: spurious network error (1 tries remaining): curl error: Could not resolve host: github.com
; class=Net (12)
error: failed to fetch `https://github.com/rust-lang/crates.io-index`

Caused by:
  curl error: Could not resolve host: github.com
; class=Net (12)
debian/rules:9: recipe for target 'override_dh_auto_build' failed
make[1]: *** [override_dh_auto_build] Error 101

[Colin Watson (cjwatson)]

I'm afraid that external internet access is intentionally not allowed in Launchpad recipe builds. You'll need to arrange to package the dependencies you need, build-depend on them, and get cargo to use them.

Build-depending on dh-cargo and using "dh $@ --buildsystem=cargo" may be helpful; if you follow https://wiki.debian.org/Teams/RustPackaging/Policy then it should also be possible to build your package on Launchpad.