devtool: check locale and refuse to start if it isn't UTF-8

We need to ensure the locale is UTF-8 or otherwise strange errors will
occur later on during execution - the same reason we check this in
BitBake itself. Unfortunately this check has to be before command line
parsing and therefore showing the help text in response to --help, since
that relies upon parsing bitbake's configuration (as we need to load
plugins in other layers).

Fixes [YOCTO #10908].

(From OE-Core rev: 370c6ba16c72bb52e80da098a5812ed1e09ac659)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/devtool

@@ -215,6 +215,9 @@ def main():
     global config
     global context
 
+    if sys.getfilesystemencoding() != "utf-8":
+        sys.exit("Please use a locale setting which supports utf-8.\nPython can't change the filesystem locale after loading so we need a utf-8 when python starts or things won't work.")
+
     context = Context(fixed_setup=False)
 
     # Default basepath