clarify error message when no image is generated

1 files changed, 5 insertions, 1 deletions

diff --git a/tests/test_pretty_print.py b/tests/test_pretty_print.py
index 8c13c62..3f4f1c9 100755
--- a/tests/test_pretty_print.py
+++ b/tests/test_pretty_print.py
@@ -319,10 +319,14 @@ def png_encode64( fname, width=250 ):
 		data = ''
 	data_uri = data.encode("base64").replace("\n","")
 	tag  = '<img'
+	tag += ' style="border:1px solid gray"'
 	tag += ' src="data:image/png;base64,'
 	tag +=   data_uri + '"'
 	tag += ' width="'+str(width)+'"'
-	tag += ' alt="openscad_test_image"'
+	if data =='':
+		tag += ' alt="error: no image generated"'
+	else:
+		tag += ' alt="openscad_test_image"'
 	tag += ' />\n'
 	return tag