Throw on bundle.formatPattern if errors would be swallowed

[Pike]

bundle.format and soon, bundle.formatPattern swallow errors if you don't pass in an errors array.

We should throw on errors instead, I think.

[stasm]

Do you think we should:

1. throw to complain that errors were not passed as an argument, or…
2. change the error reporting mode and throw a special kind of error containing the array of collected errors?

[Pike]

... or ...

3. throw the first error
4. throw the last error

I'd not do 1, I didn't think about 2.

[eemeli]

I'd vote for option 3. At that point, no matter what the specific error, showing some fallback string like the message key in the UI is probably at least pretty close to the least wrong thing to do, while printing the error in the console. If the library user wants to do something more complicated than that, that's exactly what the errors argument is for.

[stasm]

Fixed in #396 on the release branch.