TOML reading should be independent from locale settings

[dahlia]

According to TOML specification:

A TOML file must be a valid UTF-8 encoded Unicode document.

The current implementation implicitly decodes the bytes from a package.toml file according to the system locale settings (e.g., LOCALE, LC_ALL).

Scan error: ./package.toml: hGetContents: invalid argument (invalid byte sequence)

[AlanSynn]

on going

[AlanSynn]

Couldn't get approaches to set LOCALEs on mac. (e.g. Latin1, EUC-KR, CP949)
If you want to make a further progress, then set a docker environment for Linux.

Further Progress
The experiment should be performed with package.yaml containing some non-ascii characters.
Reproduced on Linux(Docker), not on OSX.