Enable pytest pre-commit

Change-Id: Ia00a9fa0d260c68ce8532dec9925467558fe7dea
Signed-off-by: Jeremy Johnson <jeremy.johnson@arm.com>
diff --git a/scripts/py-dev-env.sh b/scripts/py-dev-env.sh
index 904ff80..cc5da72 100644
--- a/scripts/py-dev-env.sh
+++ b/scripts/py-dev-env.sh
@@ -15,6 +15,7 @@
 
 if [ -e "setup.cfg" ]; then
     pip install -e .
+    pip install pytest
     export PYTHONPATH=$PWD/scripts:$PWD/thirdparty/serialization_lib/python
     echo "Set PYTHONPATH=$PYTHONPATH"
 else