Run all PREUPLOAD in virtualenv

This avoids having to install things globally.

Bug: None
Test: Uploaded this CL.
Change-Id: Iad0aad45785fc3185f6887df8aacb98e7363e495
diff --git a/PREUPLOAD.cfg b/PREUPLOAD.cfg
index a62e1f9..5260bc1 100644
--- a/PREUPLOAD.cfg
+++ b/PREUPLOAD.cfg
@@ -1,7 +1,7 @@
 [Hook Scripts]
-yapf_hook = ./tools/yapf_checker.py
-proto_check = ./tools/proto_check.py
 create_virtualenv = ./tools/create_virtualenv.sh
+yapf_hook = /tmp/acts_preupload_virtualenv/bin/python3 ./tools/yapf_checker.py
+proto_check = /tmp/acts_preupload_virtualenv/bin/python3 ./tools/proto_check.py
 acts_unittests = /tmp/acts_preupload_virtualenv/bin/python3 ./acts_tests/tests/meta/ActsUnitTest.py
 destroy_virtualenv = rm -rf /tmp/acts_preupload_virtualenv/