Change some tests to use buttercup

[ckoparkar]

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[ckoparkar]

Start fixing #1650
A bulk of the tests are still not migrated. I'll submit separate PR for some of the larger files.

[Malabarba]

Is this lambda really necessary? Doesn't it work if you just write the code to be executed?

[ckoparkar]

I believe it is necessary for the to-throw matcher. Otherwise the error is not handled and the tests fail with error: (user-error "nil needs an active nREPL connection").

[bbatsov]

You'll have to update the travis config to run the buttercup tests and the ert tests. Otherwise we can't make a staged migration to buttercup.

[ckoparkar]

Done. Have squashed everything into a single commit and rebased against the latest master. Also, should we mention the migration somewhere in the contributing guide, or somewhere else ? So that newer PR's would use buttercup instead of ert.

[ckoparkar]

I've changed some more files, but din't include them here because this PR has gotten big enough. Will submit follow up PR's.

[bbatsov]

Also, should we mention the migration somewhere in the contributing guide, or somewhere else ?

After the migration is ready we can add something about this in the docs. Hopefully the migration won't take long - we don't have many tests.

[Malabarba]

Cool. Thanks for the effort and patience. :-)

[ckoparkar]

Thanks @Malabarba 🎉