Add clean error message when RAILS_ENV is unset

[ClearlyClaire]

By default, an unset RAILS_ENV is understood as RAILS_ENV=development.

However, this is not what most people expect, and due to development-only dependencies, users are often left with confusing error messages.

This commit changes it so that an explicit RAILS_ENV is required, and failing that, an error message is displayed before loading the app.

[mjankowski]

I realize this is ~2+ years ago ... has this been a largely positive change?

For my personal workflow -- the defaulting to development seems fine; the test setup helpers explicitly set things to test; and I'd expect anyone running a production server to be comfortable explicitly setting env vars appropriately.

I'm curious what the background issues here were that users had confusing error messages ... was this confusion amongst people doing local development, or actual users of running production servers which had been misconfigured?

[ClearlyClaire]

I realize this is ~2+ years ago ... has this been a largely positive change?

Hard to say, but I'd say it has been, since we haven't seen anyone confused by that addition, and stopped receiving people posting tracebacks that were due to running commands against a dev environment instead of a production one.

I'm curious what the background issues here were that users had confusing error messages ... was this confusion amongst people doing local development, or actual users of running production servers which had been misconfigured?

The confusion was from admins trying to run commands in production environments but without setting RAILS_ENV. This would be mostly errors about some (dev-only) dependencies not being found, which can be highly confusing.

[mjankowski]

Cool, thanks for explanation and glad to hear it's reduced confusion on admin side.