From 7dc0928f52eb5ab795292d300808aac06b4564b5 Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Fri, 18 Mar 2022 10:40:47 -0700
Subject: [PATCH] graphviz: show error when lacking permissions

---
 graphviz.tlv | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/graphviz.tlv b/graphviz.tlv
index 3757c0b..54a6404 100644
--- a/graphviz.tlv
+++ b/graphviz.tlv
@@ -501,11 +501,13 @@
 - __teliva_timestamp: original
   read_dot_file:
     >function read_dot_file(filename)
-    >  local infile = start_reading(nil, filename)
-    >  local chars = graphviz_buffered_reader(infile)
-    >  local tokens = graphviz_tokenizer(chars)
     >  local graph = {}
-    >  parse_graph(tokens, graph)
+    >  local infile = start_reading(nil, filename)
+    >  if infile then
+    >    local chars = graphviz_buffered_reader(infile)
+    >    local tokens = graphviz_tokenizer(chars)
+    >    parse_graph(tokens, graph)
+    >  end
     >  return graph
     >end
 - __teliva_timestamp: original