rails/rails — comment on commit 12be0a59856d4f92a85c479843e296342be47789
File:  line 0
By sikachu:

Correct me if I'm wrong, but I think it is to make the string immutable, as we wouldn't want someone to play around with that constant right?

```
irb(main):001:0> FOO = 'foo'
=> "foo"
irb(main):002:0> FOO.sub!(/.+/, 'bar')
=> "bar"
irb(main):003:0> FOO
=> "bar"
irb(main):004:0> FOO.freeze
=> "bar"
irb(main):005:0> FOO.sub!(/.+/, 'baz')
TypeError: can't modify frozen string
from (irb):5:in `sub!'
from (irb):5
```