check for debugging lint in CI (#2578)

* check for debugging lint in CI
* nit
* add TODO

ci/nits.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+#
+# Project nits enforced here
+#
+set -e
+
+cd "$(dirname "$0")/.."
+source ci/_
+
+# please don't print from --lib...
+declare prints=(
+  'print!'
+  'println!'
+  'eprint!'
+  'eprintln!'
+)
+
+if _ git grep "${prints[@]/#/-e }" src
+then
+    exit 1
+fi

ci/test-checks.sh

@@ -13,6 +13,7 @@ _ cargo fmt --all -- --check
 _ cargo clippy --all -- --version
 _ cargo clippy --all -- --deny=warnings
 _ ci/audit.sh
+_ ci/nits.sh || true # TODO: remove || true once all println!s are expunged
 _ book/build.sh
 
 echo --- ok