Migartion removing index column fails

[daviian]

• Gitea version (or commit ref): 4b2c8ca
• Git version: 2.7.4
• Operating system: Ubuntu 16.04
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

2017/10/04 12:15:46 [I] Migration: remove index column from repo_unit table
2017/10/04 12:15:46 [...itea/routers/init.go:55 GlobalInit()] [E] Failed to initialize ORM engine: migrate: do migrate: DROP COLUMN index: Error 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'index' at line 1

Description

Migration removing index column from repo_unit table fails with above error.

[lafriks]

Index is reserved keyword and has to be escaped