maybe this will help

76ebf927 · Kenneth Reitz · 3c3e6210 · 76ebf927
Commit 76ebf927 authored 9 years ago by Kenneth Reitz
--- a/bin/steps/pip-install
+++ b/bin/steps/pip-install
@@ -9,6 +9,7 @@ set +e
 PIP_STATUS="${PIPESTATUS[0]}"
 set -e

+cat $WARNINGS_LOG > /dev/null
 show-warnings

 if [[ ! $PIP_STATUS -eq 0 ]]; then