Fix error when running under radian

[t-kalinowski]

closes #1668

[randy3k]

Tested on macOS, works perfectly. Thank you for the quick fix.
Though I wonder why you want to skip windows. radian was working perfectly fine on windows too.

[t-kalinowski]

Thanks! I replied about the Windows question here: 817c988#r146786827

[t-kalinowski]

Thank you, @randy3k!

I believe I understand what was happening and have pushed another fix. With this branch, radian should now work on all platforms again, including Windows. Would you be able to run Radian CI tests against this branch to confirm?

[randy3k]

Perfect, all tests pass randy3k/radian#490.
Thank you for the quick response.