当我尝试使用本地焦点镜像或设置代理时，它会失败。这是安装日志片段：
2020-12-01 13:47:16,916 DEBUG root:39 start: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks: configuring installed system
2020-12-01 13:47:16,918 DEBUG root:39 start: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/000-configure-run: running '/snap/bin/subiquity.subiquity-configure-run'
2020-12-01 13:47:16,919 DEBUG root:39 finish: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/000-configure-run: SUCCESS: Status.SUCCESS
2020-12-01 13:47:16,925 DEBUG root:39 start: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/001-configure-apt: running '/snap/bin/subiquity.subiquity-configure-apt /snap/subiquity/1966/usr/bin/python3 true'
2020-12-01 13:47:17,503 DEBUG root:39 start: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/001-configure-apt/cmd-apt-config: curtin command apt-config
2020-12-01 13:47:17,508 DEBUG root:39 finish: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/001-configure-apt/cmd-apt-config: SUCCESS: Status.SUCCESS
2020-12-01 13:47:18,405 DEBUG root:39 start: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/001-configure-apt/cmd-in-target: curtin command in-target
2020-12-01 13:47:32,907 DEBUG root:39 finish: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/001-configure-apt/cmd-in-target: SUCCESS: Status.FAIL
2020-12-01 13:47:32,909 DEBUG root:39 finish: subiquity/InstallProgress/install/curtin_install/cmd-install/stage-curthooks/001-configure-apt: SUCCESS: Status.FAIL
2020-12-01 13:47:32,911 …