localrepo: don't attempt to open .hgtags twice if the error isn't ENOENT

mercurial/localrepo.py

@@ -272,7 +272,9 b' class localrepository(repo.repository):'
 
         try:
             fp = self.wfile('.hgtags', 'rb+')
-        except IOError:
+        except IOError, e:
+            if e.errno != errno.ENOENT:
+                raise
             fp = self.wfile('.hgtags', 'ab')
         else:
             prevtags = fp.read()