Resolve security vulnerability. am: ed1d1ad4c0 am: fdce3c4cc7

Original change: https://android-review.googlesource.com/c/platform/tools/test/openhst/+/2375477

Change-Id: I61e7596c0a1dedb2e51a7af2fd24d3f25b228e08
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/start_venv.sh b/start_venv.sh
index cc2af8e..fe6ecf4 100644
--- a/start_venv.sh
+++ b/start_venv.sh
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 #!/bin/bash
-python -m pip install wheel
-python -m pip install requests
-python -m pip install --upgrade requests
-python -m pip install -r requirements.txt
+python -m pip install --require-hashes wheel
+python -m pip install --require-hashes requests
+python -m pip install --require-hashes --upgrade requests
+python -m pip install --require-hashes -r requirements.txt