gitea: Gitea cannot start with a read-only config

• Gitea version (or commit ref): 1.7.0-rc2
• Git version: NA
• Operating system: Arch Linux with Docker 18.09
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io: NA
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

2019/01/11 19:34:13 [...s/setting/setting.go:941 NewContext()] [E] Error saving generated JWT Secret to custom config: open /data/gitea/conf/app.ini: permission denied
2019/01/11 19:34:14 [...s/setting/setting.go:941 NewContext()] [E] Error saving generated JWT Secret to custom config: open /data/gitea/conf/app.ini: permission denied

Description

Running with the exact same configuration and on 1.6 latest docker image does not give this error.

The configuration file does have the following lines:

LFS_START_SERVER = true
LFS_CONTENT_PATH = /data/gitea/lfs
LFS_JWT_SECRET   = ${lfs-jwt-secret}