buffering=1 not allowed with binary files

This fixes #534
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 056904a..f0217e6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,5 @@
 ## Changes in 0.12:
+- Bug: buffering=1 not allowed with binary files (#534)
 - Bug: Invalid mailing list address supplied (#516)
 - Enh: stats.lua could return monthly stats to show in calendar (#532)
 - Bug: archiver.py msgbody() function issues (#244 and #463)
diff --git a/tools/import-mbox.py b/tools/import-mbox.py
index 28c0363..59f94f8 100755
--- a/tools/import-mbox.py
+++ b/tools/import-mbox.py
@@ -161,7 +161,7 @@
                             bmd = bf.read()
                             bf.close() # explicit early close
                             bmd = gzip.decompress(bmd)
-                            tmpfile = tempfile.NamedTemporaryFile(mode='w+b', buffering=1, delete=False)
+                            tmpfile = tempfile.NamedTemporaryFile(mode='w+b', delete=False)
                             tmpfile.write(bmd)
                             tmpfile.flush()
                             tmpfile.close()
@@ -514,7 +514,7 @@
         for mlist in re.finditer(ns, data):
             ml = mlist.group(1)
             mldata = urlopen("%s%s" % (source, ml)).read()
-            tmpfile = tempfile.NamedTemporaryFile(mode='w+b', buffering=1, delete=False)
+            tmpfile = tempfile.NamedTemporaryFile(mode='w+b', delete=False)
             try:
                 if ml.find(".gz") != -1:
                     mldata = gzip.decompress(mldata)