At Wed, 26 Sep 2018 15:57:12 -0700, Jordan Johnson wrote:
> > (require racket/sandbox)
> > (make-evaluator "beginner-lang.rkt")
> . . ../../../../../../../../Applications/Racket 
> v7.0/collects/racket/private/kw-file.rkt:102:2: open-input-file: `read' 
> access 
> denied for /Users/jteach/Library/Racket/7.0/pkgs/.LOCKpkgs.rktd

That was a problem with creating a sandbox in DrRacket, as opposed to
`racket` at the command line or with the handin server. It's fixed for
the next release.

> In doing a trial run of submitting my test solutions, I found my checker.rkt 
> signaling errors from the check: form: Using :language '(special 
> htdp-beginner), I get an error from the student’s (require 2htdp/image) line, 
> saying that image? is being imported twice.

Long story short, this appears to be a bug in the sandbox evaluator
setup, too, also fixed for the next release.

A workaround is to use `'lang/htdp-beginner` as the language instead of
`'(special beginner)`. That happens to avoid a redundant and
troublemaking `require`.

Roughly, the problem was that with `'(special beginner)` or `'(lib
"lang/htdp-beginner.rkt")` the sandbox constructs a module that uses
the language --- but also `require`s the language. That redundancy is a
problem if there are bindings that other `require`s are intended to
shadow, such as `image?` shadowed by requiring `2htdp/image`.

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