Propagate env vars to sudo invocations.
From the sudo man page:
```
-E, --preserve-env
Indicates to the security policy that the user wishes to preserve their existing environment
variables.  The security policy may return an error if the user does not have permission to
preserve the environment.
```
@@ -11,5 +11,5 @@ fi
source "$KOKORO_GFILE_DIR/common.sh"
cd github
-yes | sudo pip3 install ruamel.yaml
+yes | sudo -E pip3 install ruamel.yaml
python3 runtimes-common/appengine/runtime_builders/template_builder.py -f "${KOKORO_GFILE_DIR}/${CONFIG_FILE}"
