category_graph: use f-strings for style

Change-Id: I491147856ccf6e4b9751dcf3e6c062f5e503763e
---
M scripts/category_graph.py
1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/scripts/category_graph.py b/scripts/category_graph.py
index cd810a3..0110480 100755
--- a/scripts/category_graph.py
+++ b/scripts/category_graph.py
@@ -73,11 +73,11 @@
         self.leaves = set()
         self.counter = 0
         font = 'fontname="Helvetica,Arial,sans-serif"'
-        style = 'rankdir=LR ranksep=2 concentrate=true ' + font + \
-                'node [newrank=true shape=plaintext ' + font + ']' \
+        style = 'graph [rankdir=LR ranksep=2 concentrate=true %s] ' \
+                'node [newrank=true shape=plaintext %s] ' \
                 'edge [arrowhead=open labeldistance=3 ' \
-                'labelfontcolor="#00000080" ' + font + '] ' \
-                + args.style
+                'labelfontcolor="#00000080" %s] ' \
+                % (font, font, font) + args.style
         self.dot = pydot.graph_from_dot_data('digraph {' + style + '}')[0]
         self.dot.set_name('"' + cat_title + '"')
 

