distro: allow distro to specify a default locale

Currently the cloud-init default locale (en_US.UTF-8) is set by
the base datasource class.  This patch allows a distro to overide
the fallback value with one that's available in the distro but continues
to respect an image which has preconfigured a locale.

- Distro object now has a get_locale method which will return a
  preconfigure locale setting by checking the distros locale system
  configuration file.  If not set or not present, return the default
  locale of en_US.UTF-8 which retains behavior of all previous cloud-init
  releases.
- Apply locale now handles regenerating locales or system configuration
  files as needed.
- Adjust apply_locale logic to skip locale-regen if the specified LANG
  value is C.UTF-8,C, or POSIX; they do not require regeneration.
- Further add unittests to exercise the default paths for Ubuntu and
  non-ubuntu paths to validate they get the LANG expected.

1 files changed, 3 insertions, 0 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index 807b3ea2..b714b9ab 100755
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -188,6 +188,9 @@ class Distro(object):
     def _get_localhost_ip(self):
         return "127.0.0.1"
 
+    def get_locale(self):
+        raise NotImplementedError()
+
     @abc.abstractmethod
     def _read_hostname(self, filename, default=None):
         raise NotImplementedError()