build+ci: switch to python3

Also in this commit:
 * Sync CI scripts with other projects
 * Improve README.md

Refs: #5095
Change-Id: I0972967e92bdf78b8ab7cda0d9db262e38c8b32b
diff --git a/.jenkins.d/30-coverage.sh b/.jenkins.d/30-coverage.sh
index 92a9ceb..46a6d70 100755
--- a/.jenkins.d/30-coverage.sh
+++ b/.jenkins.d/30-coverage.sh
@@ -1,10 +1,5 @@
 #!/usr/bin/env bash
-set -e
-
-JDIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
-source "$JDIR"/util.sh
-
-set -x
+set -ex
 
 if [[ $JOB_NAME == *"code-coverage" ]]; then
     gcovr --object-directory=build \