capture stderr of pip-install too

bin/steps/pip-install

@@ -5,7 +5,7 @@ puts-cmd "pip install -r requirements.txt"
 [ "$FRESH_PYTHON" ] && bpwatch start pip_install_first
 
 set +e
-/app/.heroku/python/bin/pip install -r requirements.txt --exists-action=w --src=./.heroku/src --disable-pip-version-check --no-cache-dir | cleanup | log-output | indent
+/app/.heroku/python/bin/pip install -r requirements.txt --exists-action=w --src=./.heroku/src --disable-pip-version-check --no-cache-dir 2>&1 | cleanup | log-output | indent
 PIP_STATUS="${PIPESTATUS[0]}"
 set -e