What is causing this ActiveRecord::ReadOnlyRecord error?

What is causing this ActiveRecord::ReadOnlyRecord error?

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Rails :dependent => :destroy VS :dependent => :delete_all

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Rails - Best-Practice: How to create dependent has_one relations

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Rails: ActiveRecord query based on association value

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Getting fields_for and accepts_nested_attributes_for to work with a belongs_to relationship

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FactoryGirl override attribute of associated object

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Rails 4: How to use includes() with where() to retrieve associated objects

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Rails belongs_to association (with :class_name) returns nil

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Rails 3: validate presence of at least one has many through association item

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Ruby on rails: Creating a model entry with a belongs_to association

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Rails 4 Migration | Add Table with Reference

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Rails acts_as_paranoid and has_many :through

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Rails: :inverse_of and Association extensions

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How can I have two columns in one table point to the same column in another with ActiveRecord?

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Find the associations for an ActiveRecord class at run-time?

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