Fix broken examples

[dmontagu]

Change Summary

Fixes a handful of broken examples in the docs, and adds a make recipe test-examples that can be used to identify which examples are broken.

Some of them explicitly claim they will error, so I didn't set up any sort of pass/fail test, and didn't add the recipe to any of the CI or similar. But at least with this recipe you can quickly get a list of the failures and confirm there are no surprises.

I suppose we could add validation that the failures are the exact files we expect, but I figured I'd keep this change small.

Checklist

• Unit tests for the changes exist
  N/A ?

• Tests pass on CI and coverage remains at 100%

• Documentation reflects the changes where applicable

• changes/<pull request or issue id>-<github username>.rst file added describing change
  (see changes/README.md for details)

[codecov]

Codecov Report

Merging #753 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #753   +/-   ##
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  Coverage     100%   100%           
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  Files          15     15           
  Lines        2723   2723           
  Branches      536    536           
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  Hits         2723   2723

[samuelcolvin]

thanks, as you say I think we should run all example scripts in CI.

The simplest way of denoting if they should fail would be either to include --ValidationError indicating the error they should fail with in the file name. There are a few other options, but that seems simplest.