pre-upload: add missing space in the message

BUG=None
TEST=`./pre-upload_unittest.py` passes

Change-Id: I4153278dbd4372794c96ec8e800f453057d5c4ca
Reviewed-on: https://chromium-review.googlesource.com/271643
Reviewed-by: Dan Erat <derat@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/pre-upload.py b/pre-upload.py
index 4a077cd..cd75d79 100755
--- a/pre-upload.py
+++ b/pre-upload.py
@@ -707,7 +707,7 @@
         'If the ebuild should be marked unstable (normal for '
         'cros-workon / 9999 ebuilds):\n'
         '  KEYWORDS="~*"\n'
-        'If the ebuild needs to be marked for only specific arches,'
+        'If the ebuild needs to be marked for only specific arches, '
         'then use -* like so:\n'
         '  KEYWORDS="-* arm ..."\n' % '\n* '.join(bad_ebuilds))