Custom testthat skipper to skip tests if vcr is turned off via the
environment variable VCR_TURN_OFF.
Details
This might be useful if your test will fail with real requests: when the cassette was e.g. edited (a real request produced a 200 status code but you made it a 502 status code for testing the behavior of your code when the API errors) or if the tests are very specific (e.g. testing a date was correctly parsed, but making a real request would produce a different date).