我在运行rails db：migrate时遇到此错误
== 20170611143359 AddCauseOfDeathToUsers：迁移============================ -add_column（：users，：cause_of_death，：string） 耙子流产了！ StandardError：发生错误，此错误和所有后续迁移均被取消：
SQLite3 :: SQLException：重复的列名称：cause_of_death：ALTER TABLE“ users”添加“ cause_of_death” varchar
/home/peter/Desktop/morguemanger-master/db/migrate/20170611143359_add_cause_of_death_to_users.rb:3:in change'
/home/peter/.rbenv/versions/2.6.1/bin/bundle:23:in load'
/home/peter/.rbenv/versions/2.6.1/bin/bundle:23:in <main>'
ActiveRecord::StatementInvalid: SQLite3::SQLException: duplicate column name: cause_of_death: ALTER TABLE "users" ADD "cause_of_death" varchar
/home/peter/Desktop/morguemanger-master/db/migrate/20170611143359_add_cause_of_death_to_users.rb:3:in change'
/home/peter/.rbenv/versions/2.6.1/bin/bundle:23:in load'
/home/peter/.rbenv/versions/2.6.1/bin/bundle:23:in'
SQLite3 :: SQLException：重复的列名称：cause_of_death
/home/peter/Desktop/morguemanger-master/db/migrate/20170611143359_add_cause_of_death_to_users.rb:3:in change'
/home/peter/.rbenv/versions/2.6.1/bin/bundle:23:in load'
/home/peter/.rbenv/versions/2.6.1/bin/bundle:23:in`'
任务：TOP => db：migrate
（通过使用--trace运行任务来查看完整跟踪）