Issue #1999 has been updated by Hongli Lai.

File tempfile-creation-error.diff added

Here is a patch which implements the CreationError exception class, as documented in the Tempfile API documentation. However, I could not write a unit test for it because there seems to be no mocking/stubbing framework that I could use.
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http://redmine.ruby-lang.org/issues/show/1999

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