Pin pytest in test_sdists.sh. (#6764)

* pin pytest in test_sdists.sh.

* Use pip_install.py in test_tests.sh.

tests/letstest/scripts/test_sdists.sh

@@ -12,6 +12,8 @@ export VENV_ARGS="-p $PYTHON"
 # setup venv
 tools/_venv_common.py --requirement letsencrypt-auto-source/pieces/dependency-requirements.txt
 . ./venv/bin/activate
+# pytest is needed to run tests on some of our packages so we install a pinned version here.
+tools/pip_install.py pytest
 
 # build sdists
 for pkg_dir in acme . $PLUGINS; do

tests/letstest/scripts/test_tests.sh

@@ -1,18 +1,20 @@
 #!/bin/sh -xe
 
-LE_AUTO="letsencrypt/letsencrypt-auto-source/letsencrypt-auto"
+REPO_ROOT="letsencrypt"
+LE_AUTO="$REPO_ROOT/letsencrypt-auto-source/letsencrypt-auto"
 LE_AUTO="$LE_AUTO --debug --no-self-upgrade --non-interactive"
 MODULES="acme certbot certbot_apache certbot_nginx"
+PIP_INSTALL="$REPO_ROOT/tools/pip_install.py"
 VENV_NAME=venv
 
 # *-auto respects VENV_PATH
 $LE_AUTO --os-packages-only
 LE_AUTO_SUDO="" VENV_PATH="$VENV_NAME" $LE_AUTO --no-bootstrap --version
 . $VENV_NAME/bin/activate
+"$PIP_INSTALL" pytest
 
 # change to an empty directory to ensure CWD doesn't affect tests
 cd $(mktemp -d)
-pip install pytest==3.2.5
 
 for module in $MODULES ; do
     echo testing $module