Clarify that disc_filler is no unittest

diff --git a/test/disc_filler_test.py b/test/disc_filler_test.py
index a0bb4c5..74f012f 100755 (executable)
--- a/test/disc_filler_test.py
+++ b/test/disc_filler_test.py
@@ -22,6 +22,8 @@
 
 Indulge in the luxury of assuming we have python3 here ;-)
 
+*NOT* a unittest (unittest discover only finds tests in files test_*.py).
+
 .. codeauthor:: Intra2net
 """
 
@@ -32,6 +34,7 @@ from os import fstatvfs
 
 from test_helpers import disc_fill_checked
 
+
 def main(test_dir):
     """ Main function, called when running file as script """