python: fix flake8 warnings

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I19379f25f64c64ec45f363de4af11e21ba0e0df2
diff --git a/scripts/gen_pimrules.py b/scripts/gen_pimrules.py
index 5b82cdc..7099b46 100755
--- a/scripts/gen_pimrules.py
+++ b/scripts/gen_pimrules.py
@@ -5,7 +5,6 @@
 
 import argparse
 import os
-import sys
 
 import yaml
 from mako.template import Template