env['CONTENT_TYPE'] == ""
I think unicorn (accidentially? intentionally?) solves this by defaulting to text/html... but I could be wrong:
@head[CONTENT_TYPE] ||= "text/html"
So puma could default to text/html (?).
It doesn't appear that Rack has fixed the bug even. I think I'll set to "text/plain" as the default.
Set the default content type to 'text/plain'. Fixes #63
Remove 'text/plain' hack
In my case, it was puma injecting `text/plain` as the default
Content-Type value during request processing.
See evanphx's comment on puma/puma#63