There are similar untranslated error messages like these

<pre>
app/controllers/auth_sources_controller.rb:66: flash[:error] = "Unable to connect (#{text})"
app/controllers/custom_fields_controller.rb:59: flash[:error] = "Unable to delete custom field"
app/controllers/trackers_controller.rb:58: flash[:error] = "This tracker contains issues and can\'t be deleted."
</pre>
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OK, fixed, thank you for issue.
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About these four field's Chinese translation are following:
<pre>
error_can_not_delete_custom_field: 不能删除自定义属性
error_unable_to_connect: 不能连接到 ({{value}})
error_can_not_remove_role: 该角色正在使用中, 不能删除.
error_can_not_delete_tracker: 该跟踪标签包含问题, 不能删除.
</pre>
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