If some commits in a same pull request are changing a same file, patch may failed.

[apporc]

Leave error like this: ERROR: patch '--binary' '-s' '-o' '/tmp/vTiA0BX/38' 'neutron/db/l3_db.py' < '/tmp/vTiA0BX/37'
ERROR: 1 out of 3 hunks FAILED -- saving rejects to file /tmp/vTiA0BX/38.rej