Fix locale and string encoding

[TonyCTHsu]

Why

Discovered that the string encoding is US-ASCII

root@0f792b26260a:/# irb
irb(main):001:0> "".encoding
=> #<Encoding:US-ASCII>

Locale was not set correctly:

root@0f792b26260a:/# locale -a
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_COLLATE to default locale: No such file or directory
C
C.utf8
POSIX
root@0f792b26260a:/# locale
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=en_US.UTF-8
LANGUAGE=en_US:en
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

How

Before in the build process:

RUN locale-gen en_US.UTF-8
Generating locales (this might take a while)...
Generation complete.

How success looks like after the change

RUN locale-gen en_US.UTF-8
Generating locales (this might take a while)...
   en_US.UTF-8... done
Generation complete.

Note

locale-gen generate localisation files from templates (/etc/locales.gen).

[p-datadog]

Would it be helpful to add a check that the needed locale actually got generated, i.e. locale -a|grep UTF-8, and that it's used by Ruby, e.g.

 test  "`ruby -e 'puts "".encoding'`" = UTF-8

?

[lloeki]

@p-datadog I was thinking about that as well, if only to be able to check that this PR works as expected across the board by having it checking itself instead of going through this PR's generated images manually.

Let me create a quick and stupid test harness for that.

[lloeki]

I've added a couple test cases and a test harness, failure on some older rubies is expected at this stage because of the minitest version. I'll improve a bit upon it.

EDIT: HA! It actually worked.

[p-datadog]

Awesome!

[lloeki]

Pushing images with https://github.com/DataDog/images-rb/actions/runs/9783505263