Merge ~smoser/simplestreams:fix/install-deps-apt-proxy into simplestreams:master

[Scott Moser]

tools/install-deps: respect proxy vars when calling apt.

If this tool is called by non-root, it will sudo to call apt-get.
The change here is to respect (and pass along) http_proxy variables
to sudo when they are set.

see commit message

[Dan Watkins (oddbloke)]

review: Approve

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:03332f8ecd40fc3174d0037b9784e8ce079d4bac
https://jenkins.ubuntu.com/server/job/simplestreams-ci/66/
Executed test runs:
    SUCCESS: https://jenkins.ubuntu.com/server/job/simplestreams-ci/nodes=metal-amd64/66
    SUCCESS: https://jenkins.ubuntu.com/server/job/simplestreams-ci/nodes=metal-ppc64el/66
    SUCCESS: https://jenkins.ubuntu.com/server/job/simplestreams-ci/nodes=metal-s390x/66

Click here to trigger a rebuild:
https://jenkins.ubuntu.com/server/job/simplestreams-ci/66/rebuild

review: Approve (continuous-integration)

diff --git a/tools/install-deps b/tools/install-deps
index d58adc5..eb7cd63 100755
--- a/tools/install-deps
+++ b/tools/install-deps
@@ -16,8 +16,12 @@ apt_get() {
     fi
     local emd=""
     command -v "eatmydata" >/dev/null 2>&1 && emd="eatmydata"
-    sudo DEBIAN_FRONTEND=noninteractive $emd apt-get --quiet \
-        --assume-yes "$@" </dev/null
+    sudo \
+        ${http_proxy:+"http_proxy=${http_proxy}"} \
+        ${https_proxy:+"https_proxy=${https_proxy}"} \
+        ${no_proxy:+"no_proxy=${no_proxy}"} \
+        DEBIAN_FRONTEND=noninteractive \
+        $emd apt-get --quiet --assume-yes "$@" </dev/null
 }
 
 filter_installed_packages() {