diff -r b2eb66dfd9c6 -r f5a4e14d1dd2 cubicweb/dataimport/csv.py
--- a/cubicweb/dataimport/csv.py	Tue Aug 16 14:26:41 2016 +0200
+++ b/cubicweb/dataimport/csv.py	Thu Sep 08 11:40:50 2016 +0200
@@ -33,6 +33,7 @@
     else:
         f = stream_or_filename
         f.seek(0)
+    i = 0  # useful is f is an empty file
     for i, line in enumerate(f):
         pass
     f.seek(0)