Fix rails 4.2 failing specs

[jlurena]

No description provided.

[mhgbrown]

I think what's causing the root of the problem is that setting concurrent_write doesn't re-require concurrent/promise and that's necessary for certain Ruby/Rails/whatever combinations. It looks like the only chance for it to get required is during setup. After requiring concurrent/promise explicitly in the spec helper, the build passes.

Does that sound right? I can look into ensuring that changing concurrent_write will require concurrent/promise

[jlurena]

Ah nice. Thanks..it's hard for me to test as I can't install ruby < 2.7 in my machine

[mhgbrown]

Got it, I'll get something going.

[mhgbrown]

Should we close this in favor of #70?

[jlurena]

Yeah