Add absl-py for improved flags

Change-Id: Id78d88c280ce9be94bb3c28c191212ddd1d272d7
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/tools/python/requirements.txt b/tools/python/requirements.txt
index 48b58ff..db0ec26 100644
--- a/tools/python/requirements.txt
+++ b/tools/python/requirements.txt
@@ -15,6 +15,7 @@
 validators
 yapf
 sympy
+absl-py
 pyyaml
 
 # TODO(phil): Migrate to absl-py. These are abandoned as far as I can tell.