diff -r d60678a567a9 -r 328739ea70c3 mercurial/fileset.py
--- a/mercurial/fileset.py	Tue Jun 23 22:38:21 2015 -0700
+++ b/mercurial/fileset.py	Tue Jun 23 22:20:08 2015 -0700
@@ -280,7 +280,7 @@
     try:
         # i18n: "grep" is a keyword
         r = re.compile(getstring(x, _("grep requires a pattern")))
-    except re.error, e:
+    except re.error as e:
         raise error.ParseError(_('invalid match pattern: %s') % e)
     return [f for f in mctx.existing() if r.search(mctx.ctx[f].data())]