forgot to add import statement for _.

hgext/patchbomb.py

@@ -50,6 +50,7 b' from email.MIMEText import MIMEText'
 from mercurial import commands
 from mercurial import hg
 from mercurial import ui
+from mercurial.i18n import gettext as _
 import os
 import popen2
 import smtplib