Can't run any rake command: “ERROR: 'rake/rdoctask' is obsolete and no longer supported” [closed]

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Closed 6 years ago.

I'm trying to run the rake migrate:db command and I get the following error message:

ERROR: 'rake/rdoctask' is obsolete and no longer supported. Use 'rdoc/task' (available in RDoc 2.4.2+) instead.

I tried doing other rake commands, and I got the same error. How can I fix this?

来源：https://stackoverflow.com/questions/13979550/cant-run-any-rake-command-error-rake-rdoctask-is-obsolete-and-no-longer-su